I have to agree with @exialpho. If I can save 10 (or more) minutes just by shutting off the screen, then I'll do that. Depending on how you use your device, the savings can add up. Say, for example, I'm away from a charger, and having a very important email conversation with a few people. I want to be able to check my mail, answer any questions, then go back to standby as quick as possible, saving even 10 minutes can be a big deal.