Nicad batteries, in my own experiences, are very unpredictable. It may be holding decent charges for weeks and months, and die very quickly in a way it discharges very fast one day. Left unused and discharged, it can refuse to accept charge. Over charge it once and it'll die. Discharge it too far few times and it'll die. I'm not sure about memory effect as commonly stated. There are many many Internet references but it's not clear to me they are referring to true memory effect or just a plain degradation.
I agree fully with Ian. Cheap charger does not shut off.... and end up over-charging.
With better technologies around, I would not use Nicads.