My fault really, recharging only takes like 3 hours at most and I would have it on the charger basically every night for 12 hours which will take its toll eventually. Plus I run it into the ground pretty hard with full brightness and tons of twitter/internet/gaming usage.
I thought they got rid of that ages ago?
I leave my 2 year old iPhone 4 on charge all the time and it still lasts for a couple of days.
I've even had it last for 3-4 when I've hardly used it.