Yes, I would say it has been on there awhile. You are getting your moneys worth out of it. It does not owe you a thing.

It appears the voltage regulator is still working as good as a new one.

Brushes run from $.50 to a $1.50 each depending who wants to gouge you. I get mine from an auto electric shop that rebuilds alternators; his are 50 cents a brush.

You have to take it out, why not slip in some new ones. It is simple to do. Just do not solder the leads in too short as to keep them extending properly.

Disconnect the battery first! Remove two screws. It only needs about an inch and half clearance to slip out the back.

After replacement of the two little carbon sticks, you hold a couple strips of paper or thin piece of cardboard underneath them. Set the whole works inside the hole and slip out the guides from underneath as it clears the outer housing. Some manufactures provide a hole that leads to the outside of the assembly. On those you use a small wire to hold the brushes up and pull in out after it is in the hole.

Of course, for a few moments more you could just pull the alternator off the car.

I advise this because you can take a better peek at the rotor rings. To see if they grooved excessively deep which in most cases they are not. It will give you a heads up on its overall condition. You can spin it by hand up close to your ears in order to listen to the bearings, just in case they may be getting dry. Another maintenance thing is to blow out the windings of the brush area of carbon dust and road dirt accumulation.

Alternators do a lot of work for us like nothing else can, give them TLC.
Phil