Mileage as an issue doesn't really bother me. As you can see with the mileage on the cars I've owned, I put a lot of mileage on them. Instead of buying new cars every 3-5 years and taking a huge hit on depreciation, I just drive my cars and fix them up as I go. Any used car is going to need maintenance and repairs.
Buying a car is is not just a logical purchase, it is also an emtional one. I really like the body cladding changes on the 91 and newer W124's. That alone would be enough for me to upgrade to a newer one. The newer ones also got the wood trim on the doors and dash.
I would think the 2.6 liter might be a little underpowered for a car this heavy, and would probably want to upgrade to at least a 3.0 liter, or at best, a 3.2 in the 93 300E / 94-95 E320.
If you are happy with a 2.8 liter engine, and feel comfortable that the car is in great shape, well maintained, etc., it wouldn't stop me from trading up.

Just my .02 cents.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".