Default Battery Age

Just curious, how long have users kept their battery before being replaced? I replaced my initial one after about 14 months (was covered under a radio shack warranty) and at the time it was dying extrememly fast (3 hour life, though the ROM at the time may have had something to do with it). I'm on my second battery currently and it is approaching 12 months. I think my warranty expires next month and covers one more battery replacement but so far, the battery has been pretty good. So how long do you usually keep your battery before replacing it?