Warranties are very important for laptops. If it is imperative that your laptop is working at all times, make sure you receive a good warranty with a large reputable company. If you receive a warranty from a small company, you run the risk of them not being in business if a covered problem occurs and you need to pursue a claim. Make sure you understand how the warranty works and what procedures are in place for carrying out repairs.
Because your laptop is moved from place to place, you run a higher risk of component failures than with your desktop, so it is in your interest to have a worthwhile warranty.
In general, if you buy your laptop from a major company such as Dell, IBM, HP, Apple, Sony, Toshiba, and so on, then you almost guarantee reliable customer service, a decent warranty and availability of parts and upgrades.