Good quality rechargeable batteries should stay fully charged without use for up to 12 months but if you use the batteries then of course the charge will last less.
Rechargeable batteries can usually be recharged over and over for up to 500 to 1,000 times before they stop taking a charge.
I have Duracell Rechargeable Batteries and they can stay charged for 12 months without use and last around 5 years before they start degrading where they won't stay charged or take a charge.
Buy higher quality rechargeable batteries and they should stay charged for a good long time and last a long time.
Rechargeable Batteries cost a bit more than regular non rechargeable batteries do but they do save you money over the life of the rechargeable battery because you don't have to keep buying new batteries every time they go dead.