51. I think so long as you're health is OK, you're never too old! Past 40 (and then probably past 60) you just attract different clients for different reasons. Not every man is looking for a young, size 8 sex kitten!
This with cherries on top.
Even in civvy life tops of guys don't want the young size 8.
Young guys fantasize about the milf/gilf this is something that we can easily provide.
They want the experience because they want to learn. Young girls yes, of course, they have something, otherwise, none of us would have fucked in our 20's!!
A lot of guys don't want the size 8 because they want something to hold onto. They don't want the bony ass because for some guys it is painful. Look at the market for the cuddly lady, it's huge. Of course, not all guys want this and do prefer the size 8.
What I have found that works is stay true to yourself. Don't think about what other hookers are doing. Don't try and take on a persona that isn't you. I am who I am and that's what I am selling. The punters don't like this, fine. Of course, I tried this, and omfg the extra stress it brings inst worth it, all that constant brain always staying on, it's not worth it. Chill and be yourself regardless of age or size.
I have ranged from the size 6 to the size 22 over the years, and the size and age of me haven't impacted anything.