I had an alternator go just after the dealer's mechanic overtightened
the drive belt - still in warranty - replaced at no charge. Killed
another alternator when I drove it with a belt slightly slipping - that
is an absolute no no - burns them up - replace those drive belts. In
terms of doing something to replace brushes - thought alternators had
diodes and not brushes - but what do I know.

Oh and speaking of health of alternators - a couple of winters ago
watched a good samaritan jump start some lady's Taurus - well sparks
and smoke came out of her alternator - told her to go directly to her
garage - do not turn off the engine. Jump starting is a dangerous
thing - I always disconnect my battery if I have to do that.

My sum total knowledge of alternators.