I don't know if it is an age thing that kicks in men who are over 70, but I have been musing on a good number of instances when I was offered sex with attractive young JW women, I refused in every instance, because similar to the O.P I was married to a loyal woman , and I believed in loyalty to her in return.
It was hard sometimes, in both meanings of the word !
The bullet I really missed was the girl who looking back wanted not just sex, but to wreck my marriage and have me as her husband, she had obviously calculated the Divorces (she was married too) and the possible DFing as being worth it, but she was a Witch, and may have worked out how to do it and come up smelling vaguely of roses. Because not much later she did that, got "scripturally" divorced some how, and then married a guy, a much younger JW, who had been single until then.