Can anything really make you look 20 years younger
It is the most typed version of the question and it is almost never answered honestly, because the people answering it are selling the thing they say will do it. Here is the straight version.
Nothing you put on the surface
A serum, a cream and an oil all work on the outermost layer of skin. A change of that size is a change to the structure underneath, and no cosmetic reaches it. Anything on a shelf promising a count of years is making a promise it cannot keep, and in New Zealand it is also making one it would have to hold evidence for.
What could change a face that much
Procedures done by a doctor, over time, at real cost and with real recovery. That is the honest category for that kind of change. It is worth knowing, because it draws the line clearly: if a bottle is offering the same result for the price of a bottle, the offer is the problem.
The slow things that genuinely add up
Sun, smoking and sleep, over years rather than weeks. These are the only ordinary, free things that make a large difference to how old skin looks, and none of them can be bought. Daily sunscreen is the single biggest one, and it is the least advertised precisely because there is so little margin in it.
What twenty weeks of a serum actually looks like
Skin that is holding water looks fuller and smoother, and fine lines sit in a fuller surface so they look softer. That part turns up in days rather than weeks, and it holds while you keep going and fades when you stop. Twenty weeks of it is not a transformation, it is twenty weeks of skin looking its better version. That is a real and ordinary thing to buy, and it is what we sell.
Why the number is in so many adverts
Because it works on the person reading it, and because it is rarely challenged. Treat any specific number attached to an outcome, a span of years or a percentage, as the single clearest sign that a page is selling harder than its product can support. A page that says skin looks smoother is describing something you can check.
A better use of twenty weeks
Sunscreen every morning. A cleanser that does not leave your face tight. Something hydrating at night, every night, at the same point in the evening so it becomes automatic. That is a routine you will still be doing at week twenty, and being still at it is what makes any of it show.