Ady1. I have some 600 MAh nicads that have been on continuous charge for the last 15 years (an experiment) using an Ace SUPER Smart Charger. It is a pulse charger.
The main problem with nicads (apart from venting when overcharged) is dendrites, nasty little filaments that grow between the electrodes so an occasional blast with a high current pulse blows them away.
I have some electron microscope photos of dendrites but unfortunately unable to publish them here.
Solar chargers are the way of the future, I use a solar brick to recharge my phone and drone r/c when in the bush.
* Danny M *