with NiCD's and NiMh's it doesn't really matter. If you leave them at a full charge, half charge, or something like 1.1 or 1.0v per cell because they have a self discharge rate that's pretty high. If you store them for 3 months or so, they would all be pretty much at the same state of charge anywho =)

The thing that helps them is when you store them, store them at a colder temp, like the fridge or something. Alot of them can go down below freezing, so I guess you could store them in the freezer, but personally I would store them between 40 and 55 if you can =)