The testostone level makes for better early morning gym sessions than sex, IMHO. The issue is not that your buddy is ready for sex, but that his wife is.

Women need longer to get going than we gents do. For women, sex is less about the physical than about the emotional, with exceptions (like at the beginning of a relationship or after a long abscence). It is also (this is my personal opinion rather than the above clinical findings I've listed) a lot better if you share some fantasies and imagination.

I've had multiple long-term relationships. My wife and I are together 21 years and the sex is still awesome. I think that has to do with us having the same kinks and working with each other's fantasies (and no, I won't be sharing details).

My advice to your buddy is for him to sex up his lady by getting her to talk about what gets her hot, and then run with that. Make it about her fantasies and he'll have a great time (unless her fantasy involves her husband being "trained" by a rugby team and he's not into that - I'm not judging!)