[pdxmotorhead]

Dirty battery connections are the most common culprit.
They don't have to look gross, just a thin layer of oxide will
do the trick and mess up the starter.

The thing that usually happens is the cables get dirty (or the battery gets weak)
the battery doesn't fully recharge, then when you start the car the starter
gets too hot because of lower voltage, then when it spins the overheated
armature slings the solder out and the brushes fail.

Dave