I have been using the BT keyboard for a while now and the trackpad since shortly after it first appeared. Even with hours of daily use I can sometimes go a few weeks without recharging the batteries.

Even if I forget to plug the rechargeable batteries in, If I plug them in when the keyboard or trackpad is getting low by they are done charging before the batteries in the keyboard die. I am using batteries and a charger I bought at one of the national big box stores not the ones sold at the Apple store. Works fine.