They will allow the engine to sit low on one end. That will change the angle of the half shafts which can cause a shudder in the steering wheel under acceleration, and they can let the engine rock more when changing from forward to reverse. That increases the travel of flexible exhaust parts and the flexing of wiring harnesses and hoses. None of that is severe and critical that they be replaced right away, but delaying the repairs won't gain you anything.

We don't get involved with cost because there's way too many variables. The best you can do is get a few estimates from some independent shops.

Nov.3, 2012

Dear Caradiodoc,

Thanks so much for your advice. I got several estimates for
replacement of engine mounts for my 2002 Honda Accord.
The local certified auto repair shop saved me $700 as the
dealership estimate was $2,800 plus for the same work.
Again, thank you so much for steering me in the right direction.

Retired CAJ

That still is rather depressing. My last experience was at a very nice family-owned Chrysler dealership from 1990 through 1999, so mostly what I saw was relatively new cars. Engine mounts on '70s and '80s models rarely needed to be replaced on any car other than some common failures on GM's smaller trucks. There was one mount we needed to replace with an updated one to stop an annoying thump each time the AC compressor cycled on, but that one only cost around $70.00 with parts and labor, and Chrysler paid for it. Most of those cars and minivans only had three or four mounts and to change all of them would cost less than $500.00. I guess a lot has changed in the last 12 years.