A lot of times with a no sleep weekend hackathon or a launch or something I can work a long time on the tough parts first, clearing up all the technical risk in a design with little test screens/pages/activities for example, and then the next day running on no sleep I'm still OK for testing on a dozen different phones/emulators/browsers and making forms return nice looking error messages and making all the buttons on the site look consistent, etc.. Basically you just have to delegate to your stupid hour self the lousy slog work. :)