I have the same concerns with my '91.
It has never left me stranded; the problems seem to develop
slowly, like a weeping water pump or a failing AC dashpot.
However, I did have an alternator die about 10 miles from home, and that could have been catastrophic if I had been in Hobbs, New Mexico or somewhere like that.

My biggest concern is getting parts/repairs if something on a 20-year-old MB fails. Any older car, even a beautifully maintained MB, is susceptable to a failure at any moment. If the alternator failed in New Mexico, and you were in a 1985 Chevy pickup, probably no big deal. But getting a part for an old MB could take a few days possibly.

I try to head off some of the risk by carrying a few vital spares, such as a belt, hoses, voltage regulator, etc. And I try to make sure the running gear is in great shape (hoses, electrical, accessoriy bearings, seals, flex joints, fluids) but I still hesitate to take it more than a couple hundred miles from home.

Ha, guess I'm losing my sense of adventure as I get older.

DG