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.
A good place to find replacement batteries for Dell laptops is eBay. It is possible to find batteries for less than $10, but they might not last as long as Dell-manufactured batteries.
Laptop battery life depends on a variety of factors. Typcially Dell has higher rated batteries.
They are projected to last 100,000 miles. I do not know the replacement cost.
After charging laptop it will 3 to 4 hours backup
The average life for a laptop battery is between 3 to 4 hoursand sometimes even less than 3 hours.
Samsung laptop and hp laptop batteries are really good and last very long.As my laptop give minimum of 6 hours of internet browsing .
Sump pump batteries typically last around 3-5 years before needing to be replaced.
Canon batteries typically last for about 2-3 years before needing to be replaced, depending on usage and charging habits.
A laptop battery will eventually lose it's capacity, but it should last several years at least before it does. Of course you have to be sure to follow directions on the initial charge or you can lessen it's capability.
Nikon batteries typically last around 2-3 years before needing to be replaced, depending on usage and charging habits.
You can find good batteries that last a while on Best Buy and Fry's sites. But you should know that it also depends on your laptop brand and model on how long your battery will last.
According to manufacturers, you should never remove the battery when the computer is plugged in. Removing the battery does not extend battery life because all batteries have "shelf" life and are no good after a certain time. Today's batteries actually will last longer if you keep it in the laptop.