That was a really interesting attachment! Four hours give or take sounds about right for Groucho. I've noticed that he'll groom after one of our lovebug sessions and he "grooms" me right after a shower... rubbing, licking, and the kitty sniff test (could it be the soap?). But I've also noticed he'll do the grooming thing if I catch him doing something he knows he's not supposed to do (he's convinced my hearing aid is a great new toy I'm not giving him). He also does it when he tumbles off the couch.