Many of the new smart phones, such as the HTC EVO and the Samsung Moment boast a battery life of 5.5 or 6 hours. This is pretty pathetic for longevity, but there might be something you can do to fix it.
Anecdotal evidence from the Sprint Users forum suggest that charging your phone from a USB port, rather than the wall charger, could extend the life of your battery to more than 30 hours.
The wall charger for the Samsung Moment charges the phone quickly, sending a lot of power at once. This causes the battery to heat up and hot batteries do not charge well. When the battery gets too hot, it can't hold a charge the same way and tells the phone that it is done charging when it really isn't.
The USB charger on the other hand, charges the phone more slowly. This time the battery doesn't get too hot, and the phone is able to completely charge without a problem.
Did this fix work for you? Let us know in the comments!