It's not their temptation. I know my lines, they know my lines. They've never been crossed. It's not that that worries me. Normally, it doesn't even bother me. The distancing (with one exception) wasn't me do it. It was the guy realizing that I wasn't actually going to lay him and dropping the friendship. That one exception was a guy that actually tried to physically make a move, got slapped down, and tried to do it again, earning himself a complete severing of ties.
With the temptation of the moment, we both know the limits and both know the magic phrase that means we've hit a limit ("Stop. Now.") He's even more respectful of my boundaries than I am (mostly, I believe, because of a fear of my violence and Geek's rage,) only accepting a new turn in the friendship if I initiate it, he doesn't believe it'll fuck up the friendship, and it won't cause issues between Geek and I or Geek and him, or him and his chica. Thankfully, his bounds and mine mesh very well, so that the phrase hasn't had to be used. I'm not really worried, it's more the irritation that I know I'm monogamous and wouldn't fuck up my marriage or the friendship for the world, but I still want to fuck his brains out, even just in my head.