I'm 51 and will see anyone from 18 up, though AFAIK I've only ever seen one teenager. I've seen quite a few 21-35, and they've all been fine (I do screen quite carefully to weed out the idiots, like most on here).
I actually enjoy the PIV side of sex, so if they want a few goes that's fine, but honestly, can't say I've noticed it makes all that much difference, i.e. most will pop once in 30m, maybe twice in an hour - more is pretty rare.
You probably just need to make your services clear, as I think perhaps if any generalisations could be made it's that porn has influenced the under-25s more, so some of them expect a shaved pussy, CIM, anal, facial etc. to be standard - you have to make sure they understand the type of booking they'll get from you.