You talking NiMH, NiCad?
I run the NiMH pretty low, but never fully discharge... I get several yrs out of them with regular use. They're primarily Sanyo cells that I get from Robot Marketplace.
Although, before I learned channel mixing, the continuous running hyd pumps may have drained some (I used certain batts strictly for equip) NiMH packs too quickly & some I cooked in a yr or so. They would take & hold a full charge, but I wasn't getting a full power release from them anymore, like maybe could there be one cell in ten restricting amp flow... trks & equip ran like a half charged pack from start to end.
Now with ch mix, I haven't bought any new packs in better than 5yrs.