[Zeke]

I think some wear is to be expected. Brushes were more or less designed to be replaced although I took apart a newer brushed tool that I picked from the trash and disassembled it just for grins. I found that the brushes were not really accessible in a way that it made sense to repair the tool. I tossed in back into the bin after cutting the power cord.

AFA wear on armatures, sure the commutator can get messy and needs a light cut on the lathe. You can do somewhat of a cleanup while it's in the tool The armature itself is a lifetime part of the tool. It all depends on how hard to tool was used and how hot it got. Long skinny extension cords will drop the voltage enough to make them get hotter faster. If a tool feels quite warm, you're pushing it and it needs to completely cool. Not just 5 minutes either because the armature has soaked up all that heat to the core.

High speed tools wear out bearings. I've rebuilt my Makita planer 2wice. It's the 100 model and NLA. The new ones like it approach 500. When parts become NLA for the 1100 I won't have a planer. Once you have the big boy you won't use the little ones.