Sorry for the confusion, but I said peak charger, not a fast chearger and yall are right. Charging too fast creates heat and heat kills batteries. A good peak charger had adjustable charge ratings for example on my Reedy Quasar Pro I charge my 600 mAh RX packs at 0.6 amps and it takes about an hour to charge. I discharge them at 1 amp when I cycle them which is usually once a month. If anything changes like shorter charge or discharge times, the pack becomes suspect.

With a wallwart you never know how much charge your packs have and if something went wrong with either the charger of the pack, you wont know it untill its too late.