Everything we make reaches you within a few days of being made, at full strength. The only question after that is how long it stays there, and that one has a real answer.
It is the thing people ask me most about a new bottle. How long is this at its best.
I will give you the answer before the explanation. Three to four months for the water based formulas, which is the window where the actives are doing their strongest work. The oil based ones are stable for years, and you can stop thinking about those entirely.
What you will not find is a date stamped on the bottle, and I know that reads as a missing piece of information, because every other thing in that bathroom has one. Shampoo, sunscreen, the drugstore moisturizer, the foundation. A printed date of that kind belongs to a product formulated to survive three years in a warehouse, and formulating for that costs you the ingredients you actually came for. I made the other choice.
For the record, I am the last person you should ask about making a bottle last. I am heavy handed, I always have been, and a 30ml of serum does not survive anywhere near as long in my hands as it should. Do as I say, not as I do.
Let me show you what is actually happening inside the bottle.
Why everything else in your bathroom has a date on it
A three year shelf life is not something a product earns. It is something a product is built for, and the building starts before a single ingredient goes in.
Think about what that product has to survive. A truck in July. A warehouse with no climate control. Six months on a lit shelf. Then a year in a steamy bathroom. The formulator has no idea which of those it will get, so the formula has to hold up under all of them.
You get there in three ways. A heavier preservative system than the product needs. Chelators and stabilizers to keep the whole thing chemically quiet. And, the expensive one, choosing the version of each active that survives storage rather than the version that works fastest on skin.
Vitamin C is the clearest example. Pure ascorbic acid is the form with the strongest evidence behind it, and it is also the form that oxidizes fastest. Most vitamin C on the market is oxidized inside about eight weeks and is no longer active, which means a great many of those bottles were finished before anyone opened them.
So the shelf stable route is a derivative. More stable, weaker, and dependent on your skin converting it before anything happens at all.
None of this is a scandal. It is a rational answer to a logistics problem. It just means the date on the box is a promise about distribution, not about your face. If you want the longer version of how formulation choices hide inside a label, it is in its own piece.
What actually changes inside a bottle
Three separate things happen over time, and the word "expired" collapses all three into one, which is why the conversation gets confused.
One: oxidation. Air reacting with the parts of the formula that are chemically interesting. Vitamin C, polyphenols, unsaturated plant oils. The reason these ingredients do anything for your skin at all is that they are reactive, and being reactive is also why they do their best work early. This is the one that sets the potency window, and it is the one this whole article is really about.
Two: hydrolysis. Water slowly pulling apart molecules that were assembled to be whole. Slow, invisible, and only in formulas that contain water.
Three: microbial growth. Contamination, in ordinary words. Bacteria, yeast and mold need water to live, so it is a risk in anything water based. It is the only one of the three that is a safety question rather than a strength question, and it is exactly what a preservative exists to prevent, which is why ours have one.
Notice that water is the common factor in two of the three. That is most of the answer. The water content of a formula sets its runway, more than anything else in it.
Which is why an oil based serum is stable for years, and a water based formula holds for roughly four to eight months at room temperature. Same lab, same standards, different chemistry.
What moves across that window is strength. Not safety.
We use a preservative. Geoguard ECT, eco-certified, in most of the water based formulas.
I want to be direct about that, because "preservative-free" has become a marketing phrase and it should not be. A water based product with no preservative system is not purer. It is a growth medium, and the person absorbing the consequences is you.
What I will not do is formulate for a three year shelf life. That is the choice that costs you the active.
So does skincare expire?
Not in the way the word suggests. A properly preserved product comes off its peak long before it becomes anything else at all, so the date that actually matters to you arrives much earlier than a printed expiration ever would, and it is about results rather than risk.
For ours, that is roughly three to four months from when it reaches you. Not because anything goes wrong at month five, but because that is the window where the actives are doing their best work, and the whole point of buying a serum is the work.
Separately, you may notice a formula deepen in color, soften in texture, or separate in the bottle. F144 does this reliably. So do several of the naturally pigmented formulas.
That is oxidation at the level of plant pigment, and it is a sign of what is in there rather than a sign of anything going wrong. Botanicals vary from harvest to harvest and season to season, so the color of a batch varies too. I wrote about that here, because it comes up often enough to deserve its own answer. Fresh skincare behaves differently, and that is most of what you are paying for.
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Your skin is rebuilding itself right now.
I write about how that actually works, what is happening under the surface, and the few places where you can change what comes out the other end. You never have to buy anything from me to learn it.
Why I make it weekly
Everything is made in our own lab in Las Vegas, in small batches, and I still make the batches.
We formulate weekly against real orders rather than forecasts. A serum blended on Tuesday can be on its way to you by Thursday. Nothing is warehoused, and whatever is left at the end of a week becomes the free samples that go out with orders, because the alternative is storage and storage is the thing we are avoiding.
The weekly schedule is what makes the rest of it possible. Skipping the three year shelf life is what lets me use the form of an active that works instead of the form that survives, and the only way to get away with that is to make it fresh and send it immediately.
F7 Vitamin C Radiance Serum, $62, is the one where this shows up most obviously. Fifteen percent Vitamin C with ferulic acid, which stabilizes it, plus squalane and ceramides so the barrier is supported while it works. That eight week clock on vitamin C is real, and the thing that matters is where it starts. Ours starts on a bench in Las Vegas a few days before the bottle reaches you, not in a distribution center months earlier. If you want the full picture of how it is all made, that lives on the lab page.
The bottle that is still two thirds full
Here is the pattern I see constantly. Someone buys a serum, decides it is precious, and uses it sparingly so it will last.
A year later the bottle is two thirds full and their skin looks the same as it did.
Skincare sitting in a cabinet does nothing at all. There is no version of this where a carefully rationed bottle outperforms one that got used. I would much rather you finish a bottle and watch your face change than keep one pristine.
So when I say use it within three or four months, that is not a warning. It is the amount you would get through anyway if you were using it properly, morning and night, on your neck as well, which almost nobody does.
How to store it, without making a project of it
Cool and dark is the whole instruction, and everything below is a version of it.
The refrigerator helps every product we make and helps the water based ones most, because actives suspended in water are less stable by nature. A shelf in the door is plenty.
Keep bottles out of the shower. Heat and steam are harder on a formula than time is, and a product living on the ledge in a hot bathroom ages faster than the same product in a drawer. I keep my showers much too hot in a city that is already 108 degrees, so my own bathroom is the last place anything of mine lives.
Off the windowsill, out of direct light, and cap on. Shake the ones that separate. That is it.
There is no prize for a perfect cabinet. Getting the bottle somewhere cool and then actually using it covers about ninety percent of the benefit.
The short version
What changes in a bottle over time is strength, and nothing else.
Oil based formulas are stable for years. Water based formulas have the shorter runway, roughly four to eight months at room temperature, because water is what microbes need and what slowly takes molecules apart.
Use ours within three to four months, keep it cool and dark, and refrigerate the water based ones if you have the space.
And use it generously. A full bottle a year from now is not a saving.
If you are ever unsure about something you have had for a while, email me and describe it. I will tell you where it is in its life and whether I would replace it.
