(Disclaimer: obviously I will be generalizing here - these comments are not true of every older or younger client)
Older men are more interesting! More experienced, more self confident, more skillful lovers, less hurried, (usually) more generous - and I don't mean only with money - gernerous with themselves, with their perspectives and advice, their time, etc.
Young guys, by comparison, are often in a hurry, may not be so interested in my pleasure, have to save up for a one hour session, are unlikely to be repeat or regular clients, and often want to squeeze every bit of action into the 60 minutes that they can.
I really enjoy multiple hour sessions where there is time for more than just the deed - time to connect, get to know one another, build a sense of "relationship". In my experience, older men really get this so much more, and often share the same persective.
I was having this same conversation with a friend recently, and she said, "Young guys (under 30 or so) just don't know shit about shit!".