What is sexual excess?

Non-scientific term: You will probably run into this term in the writings of sect members who are trying to frighten you about acting/feeling like a human being. Old claims that too-frequent intercourse (even in marriage) or masturbation caused most disease / ill-health were invented to scare gullible people. The term isn't used in evidence-based medicine. If you have a real life-harming obsession, a doctor can help.

It's relative: It's in the eye of the beholder. So it's usually when one partner likes sex a lot more frequently than the other.