I bought a Sears Craftsman battery powered in 1995 and it's still running ... original brushes AND battery. I primarily used it for HO slot car racing, every Thursday it was in use to clean the pick up shoes and minor other things as well. Then there was the bigger races about twice a month.
It got used around the house as well and just a few months ago I noticed the charge wasn't lasting as long as it once did. I always before re-charging it, ran the battery completely dead. One of the reasons I think it lasted so long.
Now they have much better battery systems so it's time I went shopping for a new one. I do not think they have the parts to support this one.
I have a "Dremel" brand corded unit I use for all the heavy duty cutting and such and it's still a beast, going strong too after maybe 12 or 13 years old.
~ Jeff