I have recently purchased a new digital camera which uses re-chargeable
batteries. I have not used rechargeables for 10 years and have the
following questions:

The battery pack says charge for 16-20 hours. Will I damage them if they
stay on charge for, say, 3 days or more ?

Is it advisable/necessary to use/discharge the batteries totally before
recharging, or can I recharge them when they are half used. They used to
say that rechargeables developed a "memory" - is that still true?

I've seen advertised charges that will recharge ordinary non-rechargeable
batteries. Are these any good ?

Many thanks for your patience with a non-techie type and thanks in
anticipation of your replies.

Terry W.