[chrisweekly]

Probably common knowledge but a PSA just in case:

Keeping batteries fully charged all the time makes a HUGE difference in their lifespan and ability to hold a charge. If you regularly let a battery run down under 25% you're directly contributing to the "won't hold a charge" problem.

[fencepost]

I can't speak as well to the bottom end, but if your hardware provides the option (ThinkPads generally do, at least with Windows), cap the charge at somewhere between 80 and 90% to maximize battery lifespan, and set it to not start charging unless it's at least 10-15% below that maximum charge level.

At the fully-charged end of things, think of the batteries like latex balloons - if you repeatedly fully inflate them they're going to have problems sooner than if you just mostly-inflate them every time.