Sex addict is kind of an insulting term to be honest. The correct psychological term would be hypersexual, and that is iffy too, because where do we draw the lines? the average orgasms a week for men is 4. But some men think they are hypersexual, and see a therapist because they did it 1 time a month ago. Real hypersexuality is due to a massive amount of dopamine to the brain, more than usual would 'maybe' mean hypersexual. I think you should talk to him openly about it. Or maybe both could go to couple's therapy to understand his sexuality more. Of human behavior, no behavior is more varied than our sexuality. Our brain is our biggest sex organ.

I recommend you get a book titled Sex at Dawn.