Got my Thunderbolt on the 7th. I ordered the extended battery on the 6th when I ordered the phone. I just got the battery today because it was back ordered.
To tell you the truth I don't know if I will need it. Unlike my first Thunderbolt that I got on launch and then sent back to keep the iphone, this new one I bought (full retail) on the 6th has been getting decent battery life.
I got it on the 7th and charged it all night. I activated it on the evening of the 8th (Friday). Pretty heavy use for about an hour setting it up, then I ran it until like 11pm and shut it down to charge for the night.
Saturday I woke up and my oldest dog was having a neurological issue, I ended up taking her to an emergency vet and putting her down
14 great years together.
The phone came off the charger at 7am Saturday. After googling emergency vets and calling several of them as well as my mom and some texts I lost only 10 to 15% in 3 hours or so.
After the vet and bawling my eyes out there was heavy usage from 1pm until 8pm. This time was spent taking I am sorry calls, looking at pictures of Casey in her better days from facebook and downloading about 30 songs (sad ones of course). At 9pm I had 25% left.
The phone was in use and awake for over 4 hours of data and talk, all 4G.
That was only the second full charge so I can only see it getting better. I think I am going to keep the extended battery for long business trips and such.
R.I.P. Casey May 07/10/1997 - 04/9/2011 I will never forget you.