My preference is to add pleasure to an existing caring and sexual relationship of a couple by giving the lady the enjoyment of a second pair of knowing hands and a second mouth and tongue. When her man then makes love to her, I can offer her mouth a large  (8 inch) thick cock while I stroke her breasts. I do not come easily and am not a heavy cummer. Age and build are less important than a sunny outlook on life and a sense of humour. For my part, I keep pretty fit with cross-country running. I am in the UK only about twice a year.