I worry too! People said that the EVO had bad battery life and I can't expect this phone will have any better. It actually has a smaller battery than the EVO but it does have a more efficient processor. I don't know how battery life on WiMax vs. LTE is.
It's worth pointing out that Android 2.2 is a LOT more efficient than 2.1 was, which I recall the Evo had at release (unless it released with 2.0, which was even worse) My OG Droid battery life almost doubled when I moved to 2.2. 2.3 is supposed to be another giant leap forward,although HTC is notoriously slow on those upgrades because of having to update Sense.
I've been reading the reviews on the Thunderbolt. The battery is always the issue. The battery will always be the issue because the consumer does a lot on the phone like surfing the web. With my BB Storm 2, I had to get an extended battery. It helped alot. I guess if i want to buy this phone. I will defintitely get an extended battery. The overall point with smartphones, the battery will not last as long as you want. Battery life is important. But when you're using the phone to surf the web, playing music or whatever, get an extended battery. Don't have to get it from the provider. You can purchase it anywhere like eBay or Amzazon for less.
I've had mine for a few days now and boy the battery life really stinks. It's hard for me to believe they put such a puny battery in this phone. It doesn't make sense except that they must want everyone to rush out and purchase an extended battery,cause those guys ain't dumb. other then that im enjoying the phone