I have never replaced my batteries. I have run the tool into the ground first. What I do to keep my ni-cad up is run the batteries down as far as the job let me. When I have the time to charge them, I run them dead dead. It's easy to do if you have a flash light for them. I run then til the is no light what so ever and let them sit on the charger even if they indicator says its charged. Throw the battery in the drill and be ready to snap a wrist. I have one yellow battery that is around six years old and a couple around 4.
I just picked up a 9 piece set of tools for the home and I'll likely burn them up before the batteries. Out of the dozen or so batteries I owned or used, I have had only 2 that has given up its ghost. Both tools that those batteries were on, were on their last leg. When the battery developes a memory and short cycles, I do the same thing. Problem solved.
I have several ni-cad devices and I treat them the same way. They all still run like a top. Least with lithium batteries, you won't have to do all that. It will be intesting to see how they hold up over the long hall. They don't like heat and sensitive to charge. To this day, I have not been on a single construction site that is temperate and power is top notch. Do they heat up under heavy use?
