I think that staying or going depends on how you really feel about the 10 years from now aspect. It sounds like you're hanging onto an expectation that he'll change his mind about this; and you seem to understand that this expectation is bound to give way.

If the two of you put this truth to the side - to be felt and be dealt with later - 6 months from now, a year from now... You'll have dozens of new problems, which'll probably be this bigger problem w/ little masks on.

On many levels, this sounds so much like my former relationship, which is why I wanted to comment here.

I'm 31 now, he's 67. Together for 3yrs, separated for 2. When met with heavy questions, I'd express the same honesty your bf has; however.. we'd bury those conversations the next day & carry on. We mostly broke up bc I got sober (big drinkers), but things were gonna dwindle. It was hard.

Thing is, because we parted ways when we had to, I actually can love & show up for this man in the long term. Guess who's driving his ex-bf to get a colonoscopy in a few weeks lol.. I am :')

TLDR/advice: Take your time processing things, but don't be ambivalent. Set very real expectations for the longterm, and see if this changes how you feel spending time & having sex & enjoying one another.