For some players the battery time sure can be too short, for some players even 10h time would be too short.
I personally can't play 4 or 5 hours non stop, 2 hours is about what I play max on one sitting, then I have at least hours break, usually several hours or even a day.
I haven't yet ran out of battery, but then again I haven't yet been in a place where I didn't have access to some form of electricity to charge.
Even then if I went to town to play PSP for 4 hours and then the battery dies, I really wouldn't mind at all as after that 4 hours I would want to do something else already.