It's best that you don't constantly run it down to almost nothing then recharge. THat's a protocol for older batteries that developed memories. Basically, charge hte iPad when you don't have enough power to get through the day. Some use their iPads all day every day, so they charge it every night. I charge mine a couple of times a week.
If you charge it every night then you don't have to worry about running out of power. But it's basically what works for you.