I have left I heart radio running, and it ran for a little over three hours before my phone shut down. I had a mostly full battery before that 3 hour run. I now keep a fully charged Kensington mini battery pack and charger available to get me through the work day.
Yeah, I'm not impressed with the battery life when streaming npr or pandora. If you're getting 1-2 hours out of every 25% on a 3g stream experience you're doing better than me. I haven't timed it exactly but started npr with a full battery one afternoon and after an hour or so it was down into the 30% range. That said, you can stream some media just fine on 2g (which is what I now do for the two sites/apps mentioned) and probably stretch out that use. Like the Prophet said before the 3g launch, faster data transmission comes at a cost.