I totally agree, we have discussed it so many times, that sex is not an issue in our relationship. Its one less thing we worry about, if she has a need or itch that needs to be scratched, then she goes out and does it. My ex and I argued so much about sex, unsatisfying, lack of size, stamina etc etc but my current wife have never argued about sex, because we dealt with it from the start. We even see it as an insurance policy for later in life, in case i'm dealt health issues and can't have sex at all, she knows because we've actioned her sleeping with other men its not a difficult topic later in life if she still requires good, constant sex.
I'm sure there are lots of men who later in life deal with erectile issues from diabetes, prostate cancer etc. and are unable to have sex, yet don't know how to deal with the wife having, wanting sex with someone else. It would be an emotional minefield for those who are confronted with it after 20/ 30/ 40 years of monogamy.