Um, yes? 2.5 hours is terrible. Besides a daily commute, many flights are more than 1 hour. Also, it'd be nice to not have my device die immediately if I forgot to charge it three times a day.
Besides, this seems fairly on par with other portable gaming devices currently.
On every international flight I've taken, there has been USB power but zero power outlets in coach.
The flights that didn't have USB outlets were shorter anyway, so the battery would hold.