I'm just pondering this in my idle moments (clearly I have too many!!)
Without actual 'work', obviously.
It's just that I often see people claiming (and I have no basis to disbelieve them!!) they are eg 35 but look 25.
HONESTLY, if I think about my very lovely and gorgeous friends, all roughly aged 35-50 and all very different women, NONE of us look any more than roughly 5 years younger than our actual ages.
I'm 43, and I take very VERY good care of my skin inside and out, and I think probably most people take me for about 38/39, no younger.
One stunning friend who is 50 and looks absolutely amazing, and does a lot of non-surgical stuff - honestly she still looks about 45, no younger.
This is absolutely not a criticism of ANYONE for getting older (I mean, what the fuck else are we meant to do) or of anyone for doing whatever they can/want to look younger. I'm just ever so intrigued as here I am eating avocado and using retinol and sunscreen and never smoking and never sunbathing... and I hear people saying they look a good 10 years younger than they really are.
SHOULD I BE DOING MORE???!!! 
Really I just want to look well, and rested, and not puffy and grey. I see no way I could look 33 right now. Apart from literal time-travel.