[Coda]

It's better to keep it plugged in all the time than to drain the battery really deep. Full recharge cycles are the second-worst thing you can do to a lithium-chemistry battery. (The worst thing you can do to it is overheat.)

When your laptop is plugged in, it'll disconnect the battery from the charging circuit until it drops down a few percent, then it'll top it back off. (Well-designed chargers nowadays report 100% charge even when the battery is at 90% or so just to keep you from thinking that there's something wrong.) This tiny little charge cycle hurts a little bit, but not as much as a big charge cycle, and since the laptop isn't USING battery when it's plugged in it takes it a fair amount of time to drop down that far.

The IDEAL charging pattern involves keeping your battery between 40% and 80% because the extremes are where problems come in. However, if you're doing stuff that drains battery (like playing games) then trying to keep it in that range is just going to cause you to have more total recharge cycles, which is worse than just leaving it plugged in.

If your laptop's battery is removable, the best thing you can do for it is to take the battery out and plug in your laptop when you're going to play high-requirements games, so that the battery isn't exposed to the heat or to extra charge cycles.

Now, separate from extending the battery's longevity: You might occasionally do a deep drain just to calibrate the laptop's battery sensor, but only if you know it needs it (e.g. if it says 0% for half an hour without ever dying, or if it dies while it still says 20%) because doing so reduces your battery's lifetime a little bit.