How long do laptop batteries last before you have to get a replacement one?

It depends largly on the person using the laptop. It also depends on what the laptop is functioning like. If it is used for business and is used nearly daily I would recommend having a fairly nice one that has nice RAM, good Operating System, nicely functioning software, connection, etc. So if I was recommending a buy of a new laptop, either for regular or business use it would be either a Compaq, HP (Compaq is owned by HP, so there are only about 2 laptops on the site,) DELL, or a Sony Vaio. But considering your question, generally, if it is a home computer used maybe 4 times a week you probably want to get a new one in about 3 years. For business you should have a nice laptop anyway so, generally, I would say that probably every 3 years as well. You may need to upgrade earlier, though, so, in which case, I would say that you should get one with at minimum the following: 1 GB RAM Windows XP DVD/CD Rewritable Disc Drive (Optional) 3+ USB Drives 802.11g Wireless (Virtually any built in wireless card) Pentium 4 (Intel) 17+ inch screen Output to a monitor Etc.