ORIGINAL: Rodney
One of the NASA studies showed that the best way to do long term storage on NiCad was to discharge each individual cell to zero volts using a slow discharge. Then a shorting bar was attached across each cell and then they were stored at a low temperature. I do not recall what the recommended temperature was but I think it was slightly below 30 degrees F. When ready to use them, let them warm up to room temperature and then give them a long slow charge.
Rodney, those batteries were an entirely different design than the ones we use in our hobby, mostly flat plate and semi flooded systems with gas barriers between the plates. Storing sealed wound Ni-Cds or Ni-Mh that we use in the hoob in the shorted state will cause them to leak over time.