Physical condition and appearance aside I believe it is inevitably up to both the lady and the clients she has as to what age is too high. To some 40 maybe too high, to others 50, still others may find 35 to be "over the hill." Since this conversation is not about physical appearances it is all dependant on individual tastes and beliefs as to how old is too old. I believe this industry is like every other industry. As long as you are willing and capable to perform the tasks demanded of you in your work place it should be up to you to determine when it is time to retire! Personally speaking I find a mature more experienced woman much preferable than a younger less mature girl. There are aspects of life that a mature lady can conversate with you that a younger girl may not be aware of...yet. Of course I am speaking in general terms and by no means am I lumping all ladies into two categories of "young and old." Strictly speaking I find ladies who are over, let's say 30 years of age for an arbitrary number, to be much more fun and confident than someone who is less "seasoned."