Not all charges are the same. If you discharge your batts to say 3.3 volts each time (no load), which is close to completely discharged, and then recharge you will probably get around 300 charges out of them. If you recharge them at around 3.7V, when they have around 40% left, you'll probably get around 1,000 charge cycles out of them. Here's
a page from Battery University that gives a lot more information on it all.
Performance drops slightly with every charge cycle. Other things in addition to how low you discharge your batts have a big impact on battery life also. The more amps you draw, the higher the temperature during use and charge, the quicker you charge them, the quicker they will age.