C: Chores
Just because your hothusband/hotwife is no longer interested in you for sex doesn't mean they no longer want you to be part of their lives. (In truth, they probably never really were interested in sex with you, though for too long they thought they should humour you and put up with mediocre sex.)
Not only do they love how much you love and worship them -- so much so that you gladly let them cuck you -- but they also appreciate that you're eager to pick up more of the household chores, maybe even all of them. You happily clean the kitchen while they make passionate love in the bedroom, or maybe even prepare dinner for you husband/wife and their lover.
They have a lover or lovers to satisfy their sexual urges, but you're always there to make them comfortable, take care of the household, etc.