Thats kind of an impossible question to answer. If you follow general battery care rules. I have a snap-on cordless impact that is 12 years old and still runs great on the original nicad battery. If you are the type who lets batteries drain all the way down and then charges it just enough to do what you need, then throw it in a drawer to drain again, probably not long. However if you keep tools at 50-75% charge and then top them off before use likely years and years.