Always wondered myself, so good question.
My stats: 65, married, twice a month on average, once with my ATF for a very warm and affectionate NSBR and real massage, and once for a more anything goes adventure session either midtown or C town.
Ive been at this for about 3 years, so not a lifetime pursuit, but its still a shitload of money so it has to be worth it. It is. Keeps me young.