I usually check between 1-2 times a day how much I've earned, but I bet there are people who check so much more than me.. just curious to see how often you guys log in to your accounts to check your balance.
Every 5 minutes, 24/7/365. Using Firefox extension that auto updates and displays balances in browser bar.
Since I don't earn much with AdSense, I check my earnings twice a week. If I'm lucky - I may have a dollar or two waiting for me in there.