Is everybody really playing their portables so long every day? If the battery lasts 5 hours you should be just fine. I've never played any handheld for 5 hours on one day. (And if anyone does that regularly it's clearly too much.)
If you charge it over night you shold be just fine for a whole day. In my opinion at least.
I also have a PSP and it's battery life is similar to the reported battery life of the 3DS. When the battery is full I never have to charge it throughout the day. 5 hours seems absolutely fine to me seeing how advanced gaming has become in the last years.
And if 5 hours really isn't enough you can always buy one of those external chargers.
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