in AMD, Mobile versions of the processors will last around 2 hours (Will see M after the speed),
and same goes for Pentium with 'Mobile' at the start of the rating. These will be built to last longer for laptop use
For instance, heres a list to show what I mean for Intel:
it would depend of course on use, but the 2 hour rating is usually based on a bit of hard work too, thugh if yu play games, of course this would drop a bit as it uses more power than listening to music and typing on a word processor for instance. Though you know your gettnig the max power available.
I hope this helps