I decided to get a battery grip and a pair of batteries for my 1 year old 500D. I've taken roughly 18000 images + videos in a year to give you a rough estimate of the battery condition.
In any case the spare nameless batteries I bought for 5€ each are stated 1500 mAh compared to 1080 mAh stock. I tested both batteries by checking how long I could record 720p 30fps video with the lens cap on and maximum LCD brightness. Fully charged the used Canon battery lasted a measly 35minutes. The new generic both record video for 1h and 1 minute. It seems the mAh rating is quite accurate. I don't know how many times I've charged the original battery but estimating it's certainly not more than 60 times and that's already pessimistic.
I'm very pleased with my purchase, hopefully they will last a couple of years.
