Contrary to popular belief, rechargeable batteries have a life too.. depending on the type and voltage of a battery they last for 100-40000 cycles. The most common used batteries are lith-ion batteries(1000-3000 cycles) for cell phones followed by alkaline batteries(100-1000 cycles) used for multiple purposes like in clocks, discmans etc. To get the optimum and maybe a little more out of your battery, you need to maintain and care for them. Simple things like not letting them discharge completely before charging ( rechrge when approximately 15% of its power is left) and keeping them away from extreme temperatures and moisture. Good luck !