I just got my SB-600 and was shooting a little setup for the OTAP contest and not 15-20 flashes later it stopped responding and the only indication that it wasn't completely borked was the lcd in the back had the faint neon glow on it. I put some new batteries in and it seemed to work fine. My question: How many shots can you normally get out of a freshly charged set of AA batteries? Also, what brand do you use and do you take the batteries out when you're not using the flash? Thanks!