I bought my 93 W124 (M104) in 98. It had 72.5K when purchased.
Current mileage is on my sig, and it is my daily driver. Absolutely the best daily driver I have ever owned.
It hasn't been without problems though. The evaporator, wiring harness, belt tensioner and timing cover seal were replaced at around 90K...all under an extended warranty. When the warranty expired, the entire cooling system failed one component at a time for about six months...water pump, expansion tank, thermostat, sensor, and finally, radiator. Fortunately, I had discoved this forum by then, and saved tons of $$$ doing the work myself. Otherwise, I probably would have been frustrated enough to sell it!
That was two years ago, and it's been quiet since...brake pads, tires, fluid changes is all the old W124 has asked for.
I keep an eye on that rear head leak, as I know the head gasket is on it's way out someday.
Most of the major issues should crop up between 90-150K. After that, it's just long-term wear, and that is dependent on owner use. When you do go shopping, see what of the issues I mentioned have been dealt with. The evaporator and head gasket are the two priciest repairs (read, labor intensive) if you have them done by the dealer.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car