Best to leave the Laptop Battery.Laptop Battery[/url] in all the time. Some claim that if left in the battery will run hotter and die sooner, but this just isn't true. Lifetime depends on may things. The worst thing to do is run it down all the way. This shortens battery life a lot. The new hybrid cars use Lithium batteries, and the discharge levels are kept at 50-60% to maximize life. The OEMs have to warranty the batteries and they are expensive. Number of cycles is also a major variable. I have 3 1/2 years on the original battery in my M1530, and it's still giving an hour or more battery use. When new, it was about 1 1/5 hour.