Ever wondered what makes your laptop batteries last longer? Sander Sassen from Hardware Analysis tested a couple of options. Over a period of eight months he used two identical notebooks. One has been connected to the power adapter all the time, being used for approximately eight hours every day, the other has had its battery drained and recharged, usually once a day, but has also been running for eight hours every day.
The results: the notebook that has been connected to the mains has a flat battery now, allowing about ten to twenty minutes worth of battery power before going on standby. The notebook that has had its battery cycled does not offer the plus four hours of battery life it used to give, but is still good for more than three hours of use.
While not necessarily conclusive given the small sample, it seems that having the laptop more often than not connected to the power supply could very well be putting more wear on the battery than actually draining it fully and recharging it once or twice a day. Maybe notebook manufacturers should make mention of this! But then: given the money they make on overpriced batteries, why would they tell us!