> Prolong lithium-based battery life

Lithium-ion and lithium-polymer batteries have a few key differences, according to this Battery University guide, but the main danger to laptop battery remains the same.

With the nickel-cadmium or nickel-metal-hydride batteries common in the 90s, you would need to discharge fully quite frequently to avoid the 'memory effect', which should be called the 'forgetfulness effect', because it happens when batteries forget that yes, they actually do have more power left, and quit prematurely, thinking they're out of power. That's an act of forgetting if I've ever seen one, but with lithium-ion and lithium-polymer, you don't have to worry about it; frequent shallow charges are not only safe but less stressful and healthier for the battery. You only have to discharge fully maybe once a month and that's only to give the software gauge a chance to recalibrate to the size of a full charge.

However, this is all scribbling in the margins of battery life. Charge or discharge frequency were never really the main thing killing laptop batteries. From what I have witnessed, people have just been killing their batteries by leaving the mains adapter plugged in way too long, sometimes for days. I've seen some random internetling claims that lithium batteries can be safely left docked indefinitely, but the Battery Guide article says nuts to that: forcing a battery to remain in a state of full charge with constant heat applied for an indefinite period is just a great way to age your battery chemistry at a far accelerated rate — even lithium.

Bottom line: you can read that whole article, or you can just not work with your laptop plugged in unless your battery actually needs charging. This single factor explains most of the differences I have observed between the battery life of different laptops in different environments.