After about 4 hours of being out I end up focusing on the person I'm with or fantasizing about more (not that I wasn't in the first place, but once my pleasure is dulled I have to be somewhat obsessional about the others pleasure or imagined pleasure in the case of fantasy because I've lost most of the sensitivity in the most sensitive area. If I kept it exposed at all times for virtue of not having a foreskin I'd likely not have ever found it pleasurable in the first place.