Straight alphas

Hi sam--I've been in an exclusive service relationship with a straight alpha for several years now. Thus far, he's never allowed sexual service, but he does let me massage and worship his muscles sometimes.

This weekend I was giving him a back massage, and he said "You know, if I get a serious girlfriend, we won't be able to do this anymore."

I pressed him on it, and he'd like to keep me around, but would be uncomfortable with anything physical behind his girl's back.

My question is this: what does long-term service to a straight man look like? What happens to a fag when the man enters a serious relationship? How should I navigate this once he finds someone?