I am due for an upgrade in May. I will probably get an Evo or wait for a better phone to come out. My Hero is already bad on battery (I have done everything I can to make it decent). I was wondering do you think it's a good idea to just buy an extra battery, and when my regular one goes down to say 20%, I just swap them? I was also wondering if I did carry an extra, and it was fully charged, how long would it stay 100%? I dont want to put it in and its drained from 100 to like 60 or less from just sitting in the car, or my pocket.