That is no longer true. Due to integrated graphics, most modern 17 inch laptops can offer around or over 3 hours of functional work. If you intend to game it will go back down to 45 minutes.
How modern is modern? My old 17" Core 2 Duo P8400 with Radeon graphics (i.e. not integrated), which I got shortly after the Penryn line was released, can last a little over three hours. I haven't used the battery for years though - it's sitting in my fridge.
Dunno, but the xps 17/hp envy seem to give roughly 5 and above hours for word work, if you kill the brightness and the wifi. Giving a ~3 hour life when you actually use stuff.
... you probably could get both of those things for cheaper than you'd be spending on a gaming laptop interestingly enough. And the desktop would play games better than the top of the line laptop ever could. And be way cheaper.
My point.
Also, it's easier to add to a desktop, it's not cost effective to add to a laptop.
If I lived in my hometown in my old house and didn't move around a lot, I'd be debating that a bit more. However, I do not and neither do I entertain the idea of leaving a 2k$ gaming rig in a dorm, while I go back home to visit my parents over an extended break.
I also enjoy working outside. It's not exactly uncommon for me to go out and do my coursework while sitting on a bench in the local park, in a train while going somewhere or the equivalent.
Considering that, I'm very well prepared to exchange an extra 500$ for a good instead of a superb gaming capability with the added bonus of joining a lan party while sitting a top my university's bell tower.
