The conventional wisdom is that 722.3 and 722.4 (mechanical/vacuum) transmissions are good for 200,000 to 300,000 miles. I don't have any information on the later 722.5 and 722.6 (are those the right numbers?) electronic transmissions except that the first year (1997) was supposedly less reliable.

Here is my experience:
1996 E300D (4-speed 722.4 mechanical transmission, last year for this tranny in the E-class).
249,000 miles at purchase (4th owner, November 2007).
Developed a front pump seal leak after I changed to Mobil-1 synthetic transmission fluid.
Had transmission overhauled ($2900).
Mechanic said "wear parts" (clutch packs, etc.) had another ~50,000 miles in them.
Hard parts were all undamaged and were reused.
Leak stopped.
Car now at 273,000 miles.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970