I'm guessing at 40 he'll be married with kids, right? I guess you could use this to gain position in the company, assuming you're good at the job, and then take a job elsewhere at a similar level. That would give you a leg up but get you out of the zone where folks will say you f**ked your way to the top. Don't make a habit of it. If you break up with him but stay it could go badly for you. If you stay with him & stay in the company, you'll be tainted by that "f**ked her way to the top" thing. If he's married & you get found out he'll be in deep shit & you'll be the Other Woman, the homewrecker, so best be in it for the long haul & to hell with what people say if it gets to that point.