If you leave the batteries alone for a month or more, put them back in a smart charger like BC1HU or the fancier T6278. These charge the cells individually at a fast clip. by that time they have discharged some, and some cells have discharged more than others.

Don't mix different manufacturers of rechargeables, different mAH of rechargeables, or with alkalines in a toy or product, or you could cause damage to the cells, cause leakage, or explosion due to the difference in potential. if one or more cells are discharged partially, the cell that is charged the most will reverse-charge the partially discharged cells, and then cause the aforementioned ill effects - they weren't meant to be charged backwards. so when you use them, make sure they are topped off.

beware of cheap chargers such as trickle-chargers that take 14-24 hours to charge cells - they can over-charge or under-charge, or leave one cell charged more than another. throw it away and get a smart charger. you will save your batteries.

NiCd batteries are not as good as NiMH because they have a memory for partial charges and won't charge much below the lowest charge. however, they can handle high surge currents. they also don't like staying on the charger. when using, they should be discharged fully and charged fully. see wikipedia article.

Maha Energy makes 2700mAH AA NiMH cells, the next highest (highest is 2900mAH) capacity, but the 2700mAH actually has more real power output (real mAH) in tests. lasts a long time in a most digital SLR cameras. all-battery.com sells 2600mAH NiMH cells by the boatloads (or in boxes of 4), for $1.60/AA each and they're pretty good from my experience.

If you can't wait an hour or more for the charge time, how about 30 minutes? the T8000 is a special fast charger that requires special AA 2300mAH batteries.