I was lucky to have moved from the touch pro 2 to the Evo, and since they share the same battery, I've always had a spare. I just ordered another battery off of eBay for 12 bucks with charger and free shipping. I basically don't have to think about battery life after it arrives.
I love that on the weekends that I can cycle between batteries all day long without ever needing to stop and charge the sucker.