As another matter there's a radio DJ who gets really annoyed when people possessive-ize things like Ledo (not Ledo's) and Potbelly (not Potbelly's). The thing is, some places *do* do that -- TGI Friday's, Applebee's -- and I don't feel like keeping track. I usually 's it.
Also Happy Mondays for me is in writing. I don't know if I've ever actually said it out loud.