I'm sure Trouncer (well known in the past on the site that is banned automatically) is in his eighties. When I last spoke to him he was well 'at it' and still regularly playing golf both for real and as an excuse.
I've been told by two or three SPs that they've clients in their eighties so I don't think it's uncommon.
I could understand a 20 year old woman might be a bit fazed with a client old enough to be her grandfather or even her great grandfather!
Personally, at 70 years, a 20 YO girl doesn't interest me. I prefer the 40+ cougars who are as desirous of a nice shag just as much as they want the money.