Lithium ion batteries do indeed die over time even if they're not charged, as the wiki suggests, but other than that most batteries are similar. Batteries last longest when they're never fully charged and never fully discharged. That's why batteries in hybrid cars last longer than you'd expect, they're usually in the 35-65% range. Colder temperatures also help retard deterioration. In practice though, we often keep our batteries nearly fully charged quite often, so a power cycle down to a few % is a good idea, even though we've come a long way since the nickel-cadmium days.
In practical use, if you're going to leave your laptop plugged in for a week on your desk without moving it, just let the battery wear down a bit, then pull it out and toss it on the desk next to you. If you'll be leaving it plugged in for a month, maybe you could toss it in the freezer, but we're probably looking at very small differences with the freezer methinks.
I took the battery out of my old dell laptop to help preserve it, unfortunately the power connector started acting up and then shorted the motherboard, so I'll never know if it did any good. I took the battery out of my mother's work laptop long ago because it just sits on a table. I borrowed it a while ago and stuck the battery back in - worked great, 3 hours of life in a 5 year old dell battery. of course the hinges on the screen had locked up and broke when i was using it, but listen, i already said it's a 5 year old dell.
