I do not think the kleen wheels thing is significant. Even if they did prevent cooling to any extent, this would only matter at limits, like long descents.
The 6 mile commute could be significant.
How many years did it take to get 20k miles?
Is that 6 urban miles? Urban miles are brutal.
In your climate, road grit and corrosion are rotor factors.
In other words, miles are not everything...
And hey, I have known some pretty wild-driving school teachers...
That V8 could bring out a side of her you are not familiar with.
1986 300E 5-Speed 240k mi.