Ni-Cad is old technology and if you are following the manufacturer's
recommendation you're likely going to get the best performance/longevity
(such as it is) and that't that.

Don't leave it in the charger beyond the standard charge time. Use it
to depletion each time before recharging and hope that the manufacturer
of your drill introduces a Li-Ion or Ni-MH replacementg
Yabbut nicads now days are pretty robust (not to mention longer lasting in
regards to the number of charging cycles that they will endure) Nimh have a
cycle rate of about 1/2-2/3 of what nicads will take, lion- a lot less than
the nimh. Yeah, the nimh are cheaper now and the lion are even less (or
close to it) but I've yet to hear of a lion that lasts for more than 3 yrs.
I just recycled the last of my aa nicads from circa 1974.
If the guy has that kind of problem, he should have cracked the battery
case (if it was a tool battery that he was mentioning) and looked at the
voltage of the individual cells. Me thinks he's using a dumb charger ....a
shot in the dark with virtually zero info to go on...