Thanks for the responses!
GG, We've done stuff like the people watching before, or talked about cute actors/actresses, but that's a lot more abstract than me being attracted to a guy I actually hang out with. There's no danger I'll ever be hanging out with that actor, and even given that, he seems a bit put out. Even though I tell my husband all the time that I think he's sexy, without sex backing that up all the time, I think it just seems like words to him.
I guess the 4 year itch is a possibility. I guess I thought I was already in the safe zone, because in the past, I would always get the worst puppy love at the beginning of a relationship, which would only last maybe 6 months, and usually by a year, the relationship was ending or over.
Dingedheart, I would totally be ok with him having a girlfriend of his own. Initially I thought I would only be ok with a triangle type dynamic, but reading and understanding more about poly, I think with some work I would also be fine with a V. I don't think it carries a lot of weight with him, though, unfortunately. He's your stereotypical computer geek guy, not in fabulous shape and doesn't consider himself good with ladies. So far, I've done all our unicorn hunting.