So many variables contribute to a couples experience. Their ages, length of relationship, past infidelities, presence of children, economics, health, too many to list... Everyone is different. IMO the imbalance regarding interest in sex is biological and intentional: males want to stick their dick inside anything, anywhere. Females use that fact to gain control and influence. Over time she realizes spreading her legs is less necessary to achieve her goals so her attention turns to pizza, sleeping and alcohol. Meanwhile he discovers an endless supply of vaginas are available in every corner of the globe, no matter what he looks like, as long as he has a few spare bucks.
Dude banging the wife 3 times a week is either exaggerating or they are newlyweds in their 20's and if the latter, why the hell would be trolling for hookers? At that stage of my life I had my pick of the interns, waitresses, grocery clerks and pool life guards to bop for free.