I imagine that at least half of all 190s will go to the grave with their original master cylinder. Thats just a conservative guess, it could be 80% or more. Of the scores of 190s we service I imagine we have replaced 5 cylinders.
With the advent of ABS many more people started servicing their brakes and fluid appropriately. Its always has been a problem the way MB described brake fluid replacement; "every other year in the Spring". By not placing it at certain intervals many of these fluid changes were missed. We used to do Master Cylinders in the dozens a year, now I would be surprised if we are doing over 10 a year for all the German cars we work on.
If you notice I haven't answered your question. It would be just my luck to tell you to forget it and next week have a one in a million total failure catastrophically. Not me....
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician