Some I check once or twice a month, some once or twice a year and others several times a day. In general I’ll go through our main earners (like 6 progs/networks) in the morning and again at night with an occassional check in between. Of course I’m happy to check sales notification emails as they come in. They don’t count…
Stats checking can be a huge distraction from work though. My philosophy is; I can either spend time counting my money or spend it earning more.