Bad wiring is a common issue in many other European cars. The heat in the engine compartment makes the process happen faster for the engine compartment. I have test driven MANY European cars with home brew wiring jobs that were tucked under the carpet and into door sills with make shift fuse boxes so that their tail lights and other accessories work. At least with a Mercedes you can still get parts and the engine compartment is a harness rather than just a whole car loom. The only problem is a lot of the wiring runs through the unit body so the car essentially has to be totally disassembled in order to replace the wiring inside the car. Many other European makers have a certain range of years that are hard to find. This is mostly because electrical issues have caused these cars to be parted out and only the most dedicated and patient owners have invested the time and money to fix them correctly. Some car makers are long gone and many owners have to make their own wiring harness.

Realistically the interior harness probably will last a great deal longer than the one in the engine compartment. Most of these cars are not going to start seeing major issues for many years.

I keep my cars very long term and plan ahead for many years of their service. I love 140's and even if the wiring issues had not been corrected by the 1999 revision I still would have bought one. Although the Wiring issues and A/C Evaporator were motivating factors for me looking at only 1999 model cars.