Signs of an affair: if your spouse starts working out more than ever before, buying new clothes all of a sudden, with a simultaneous lack of interest in sex with you.
I don't think being friends before romance is BS at all. My husband and I worked together and became friends (in a "group going out after work" sort of way) before we dated. But I already knew he was the one. The friendship was a prelude, of sorts. I have to say that the laughter, great conversation, and genuine caring we have for each other are the glue of the marriage. The passion is great, but it would never be enough without the friendship. I had one of those relationships, and while it was fun at first, it was never meant to last.