It may be possible to replace just the brushes in your blower motor. This has been discussed here several times over the years. The blower motor used to be available separably but not now – perhaps it is no longer manufactured. I wonder if an auto electric place could rebuilt it when necessary? In my '85, the commutator was worn so much that just replacing the brushes was clearly not going to help.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970