Gadgetress: I asked the folks at FreshBattery.com to handle this one. The Irvine e-tailer sells laptop batteries and is also a resource for people who want to get more out of their batteries.
While modern technology has enabled us to extend the life of rechargeable batteries, they only last for a certain number of ‘charge cycles’ before they lose their ability to hold a charge.
A lithium-ion notebook battery typically provides at least 300 discharge/charge cycles before its runtime is greatly diminished. How long this takes depends on how you use your notebook. Typically this will be between 1 and 3 years of use.
Keep in mind that your son can probably work with his laptop plugged in when he is home, which means he won’t be draining the battery at all. That will extend the battery’s life tremendously.
If you’re worried about the battery running out while away from a power source, you can always buy an extra one. They are pretty easy to switch out and not too expensive. You can buy a battery for a Toshiba laptop, for example, for around $100. A battery for an Apple laptop is about $129.