my rubber mounts were shot at 100K all of them, the trans mount was torn. and my jeep is still going.Longevity was never an issue for me. For example, I sure wouldn't replace my feather pillow with a wood block simply because the wood block would definitely outlast my feather pillow.
Not to mention, again, that rubber mounts typically outlast the vehicles the factory installs them into.
I'm going with poly cause thats what I went with and now the build is done.Sounds like you don't like my 'go rubber' suggestion... go with whatever you want, sounds like you want to go with polyurethane. I'm just saying I used poly before and I'll never go back to it again.