Here's another correction... I've actually been told (and it was mentioned again by one of the techs on the forum) that when it comes to brand new computers (i.e. computers within the last year), completely draining your battery can actually degrade your battery life.
Generally speaking, even with older lithium ion batteries, you only want to drain the battery completely if you need to calibrate the battery, and you only need to do this if your computer isn't recognizing the amount of battery power left correctly (i.e. it says you only have 25% left when you know there's ~50% left, etc). On older batteries it was recommended doing this once a year or when needed. On new batteries, this recommendation has been dropped by manufacturers.
I only ever recalibrated (completely drained) my battery on my old laptop two or three times, and the laptop before that twice. From what I've heard, I don't intend to do it at all on my new laptop unless I really need to. If it doesn't need to be done, don't do it. Now if you want to drain it down to 2-5% (whatever the critical level is), there is nothing wrong doing that, but avoid completely discharging it.
FYI, by doing the above, my battery power had barely degraded in the first year for both previous laptops, and I still got around 2 hours after two years (normal when new was around 2 1/2 hours).
It's okay if you discharge it to the point where your laptop automatically turns off (e.g. at 2%), but not good to discharge it all the way to 0%. To discharge all the way though, you actually have to go into your power settings and turn everything off so that the computer runs right up to the very end, so if you aren't doing that, then you're right, there's no problem.
