Back in the dark ages when those generators were on everything, it was not uncommon for one to last 30K miles or more with only routine maintenance- - - -topping off the oil cups on both ends when the engine oil was changed. At 6500 miles, the brushes will barely have any wear at all.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!