I've had several "young studs" in the past who had a problem getting it up, I assume it must be the nerves. Inexperience and lack of respect (because we sell our services) leads to inappropiate and/or degrading remarks....
I've had several older gents, whom weren't gents at all, whom also had a lack of respect issue going on and has shortchanged me.....
Bottom line for me: I personally do not put an age limit, because does it really matter if I did?
During screening, if I notice rudeness of any nature whatsoever, I do not book. It doesn't matter to me if your 18 or 65. And if I book with you, and during the session I am uncomfortable and made to feel less worthy than thou... well, lets just say your off my buddy list!!!
To the hobbyists who know how to play, thank you very much. You are what keeps me going!