Muffler donuts, how long should they last... please no jokes now.
 

I was under my 300D inspecting various things underneath and I was surprised to see the muffler donuts that I replaced last July were either broken or cracked and getting ready to break. How long should they last?

Last:
 

It seams to very. I don't know why.
They do have a different hanger for the 126. I could never get it to stretch enough to get on.
I just carry extra's.
I use a hay or boot hook to put them on.
Charlie

I used the Pep Boys generic rings in my SDs. I looped some bailing wire along with the rings to help them along. The ones in the SD seem to be made of tougher stuff.

Sixto
95 S420
87 300SDL

I thought that I had bought good quality donuts since they had "Germany" stamped on them and so I assumed that they were the OEM type. I had the rear part of the exhaust system hanging by electrical wire while I waited for the last set of donuts to arrive. I may just go back to the heavy electrical wire after this set falls apart. At least with the electrical wire I wont have worry about my exhaust system dropping off because of some failed donuts.

I replaced mine with ones from the dealer over 2 years ago. Still looking good.

Mine last a year or two.

Mine was in there for over 18 years, and it still looks good.

Original....
 

Still the originals on my '87 300SDL. Only about 72000 miles, though.

There are a lot of sources of these rubber donuts, one sells a soft rubber and another hard, I always preferred the softer rubber because its easier to install. then some are square with a plug in the center which are supposed to hold up better or something but the reality is they all eventaully crack and fail.
I have some less than 2 years old that are cracking and others that are not yet cracking after twice that period.
I remember my wife calling me in a panic once upon a time, because "something awful is wrong with the car but a man stopped and said use a coat hanger wire to fix it". I knew the muffler was dragging. I showed up with a sack full of rubber hangers and had it back in good order in a half a minute.
Actually, now that I think about it, heavy wire is probably better for the long haul, and cheaper too!
DDH

Use the rubber donut. Wire or anything like it can wear thru the hanger hooks on the muffler and the car. Donuts are cheap.

Wire doesn't stretch, either, now that I think about this more. So my recommendation is carry a coathanger in the trunk so that you will have it in case the O-ring(s) break and your muffler is dragging (BTDT)
DDH

Replaced mine last October after breaking at school. Costs $2.50 a pop from dealer, they're already cracked.

you should get the OE MB ones with the chain inside of them. They are very difficult to get on, but they last a lot longer. Rubber cracks as it is stressed, I assume you just have the standard issue rubber donuts.

The donuts with the chain I think are between 12-15 dollars each.

The ones I had were obviously the cheapo ones without any chain. These were a bit tough to get on in a couple of places as well.

Well the ones with chain are quite difficult to get on. I deceded to buy these tools below.