I have the top of my engine torn down to do the head gaskets and I was wondering if now is the time to do the engine mounts. They weren't noticeable while I was driving but with 120k on them they're probably getting tired. Would it be significantly easier with the heads and manifolds out? Not anxious to add to the cost of this refresh but I like saving time.

 

Well you could loosen at the bottom, put a block of wood on a jack under the oil pan, jack it up just a little to see if the old ones are broken (see if the mounts go up with the engine or stay down with the frame when jacking up) and if not it would be a tough call. They are way easier to get to where you're at now but, I hear you on stuff adding up.
As far as how long they usually last and when they normally go out, I guess it depends some on how hard it was ran. My 110K+ had one broken, I will replace those when I get back working on it and on the 140K+ neither was broken and I should have but didn't replace those when I was doing the HG's as I was tired of spending....I'll regret it later I'm sure but will cross that bridge when I get to it.

 

there not that hard to do with the motor in place, not a big advantage

 

If you are asking for opinions, then I would suggest just putting in new mounts now. With that said I replaced mine at 160k and they were just starting to go bad, so you probably still have some life left in them. I think it at depends on what you've been doing with your truck the last 120k. Going Off-Road often will wear out mounts and bushings way quicker then a parking lot queen.