I don't allow the email app to automatically check it at a set time, but I do compulsively check it throughout the day. If I'm focusing on a project I might go an hour or more without checking it, though. Since we work at home, if I'm away from my office I'll usually check it whenever I go to the bathroom.

For email junkies: I just started using Thunderbird 2.0 beta because it offers a limitless number of color-coded customizable tags to help organize your inbox. It really helps distinguish between what is top priority stuff and what isn't. I've got different tags for responding to fans, email requiring research, personal webmaster email, business opportunities, etc. I like it better than just sorting things into folders because you can keep everything in your inbox that still requires action and/or responses, but still sort it.