One of my sons drives a W210 that has now got well over 300K on it and is still running like new. You can see the plastics are drying out and there is some minor rust in places but it is still a very solid car and likely will continue to run for many years to come. It's the kombi version, 320.
Mechanically, it's pretty solid, absolutely. But the rust.. The rust!! And that's an issue the original galvanized W124 didn't have.
We had a W203 station as well, that one definitely was terrible (this was around the time the paint formula change happened), but the e class wagon is much older and still in very good shape. The one part that seems to be plagued by rust is the rear hatch, everything looks good. He's still debating replacing it entirely (the hatch, not the car) or welding it up and respraying it. He's a petty good welder and he really loves that car so there is a good chance he'll end up doing just that but at the same time that is not as good a fix as getting a NOS rear hatch and putting it in marine primer before spraying it.