In the "olden days," it used to be the rule to do deep discharges (meaning run the battery all the way down) and then do full recharges on occasion to extend long battery life. These days li-ion, esp. the li-ions in the past few years, seem to work best when you keep them topped off, and I've heard you can actually decrease battery life by repeatedly letting them drain to empty.
But, YMMV (your mileage may vary), every device is different, and there are tons of different Li-Ion batteries these days as well.
My Reader is coming in this weekend, and I'll probably charge mine every time I sync up, which I'm guesstimating in the beginning to be rather often. But I am probably going to try to do a long discharge once, just to see how many hours I might be able to eek out of it.
From reading the other posts, though, it sounds like the battery life is pretty excellent, so I'm guessing I'll end up just keeping it topped off via USB while I play Warcraft or something in the evenings
