I'm new to laptops....just dumb to everything else.

Store where I bought Toshiba laptop suggests buying extended warranty (surprise!!) but friendly geek kid said if for nothing else, just use it to get a "no questions asked" battery before warranty expires, if I haven't had to use it already for new battery. He said that alone would justify xtd warranty.

What kind of use-life should I expect from laptop batteries? Are they really that expensive?

Thanks