Short battery use and charge?

Has anybody had experience with replacing the battery in a Nook color e-book reader? I have tried discharging completely (to the point of the unit shutting itself off) before recharging. Also, plugging the charger in when the message pops up regarding low battery charge remaining. Nothing seems to improve my charge life of approximately 1 - 1 1/2 hour per charge. The unit is only approximately 1 year old.