Everyone needs batteries and everyone knows that it's greener and more cost effective to use rechargeables, but a lot of rechargeable batteries have issues. How many times have you recharged a set of batteries ready for when you need them, but when you actually get around to using them they are flat again? Also, there's no point in putting regular rechargeables in devices you only occasionally use, or have a very low power drain, the batteries just go flat while they sit there.
This is a pain, so I gathered up all the different types of rechargable batteries I had and replaced them with Eneloops. They advertise that even after 3 years sitting on the shelf they will still have 75% of life. I haven't tested it to this extent but I have noticed that even months after charging, when I actually need them, they are still good. They can be recharged 1500 times and come in all the usual sizes.
The strange thing is that it's rare to see them in your local store. I have been getting them from Amazon and putting them in all my devices. I even have them in my camera's flashgun which gets used only occasionally, and yet they work when I need them. So my recommendation; go order some!