like most people have said you should be absolutely fine, i've often got mine on in the office propped up next to me whilst connected to the power outlet and no problems at all so far, the battery will often last days if you're using it sporadically as well, 3hrs is about right for bright screen, wifi, net browsing / application running though if you're new to the N800 the N800 wom world might be a good resource for you to have a look at to get your head round what can be pretty complicated bit of kit sometimes