There have been reports of VT mounts failing prematurely though.
Tears in rubber and just sagging.
I guess the sagging is to a certain extend natural, as long as they do it evenly and the rubber isn't squished from between the 2 plates.
But those reports are mostly found in the US (on zpost etc).
I dont know if its the climate there or that they're all fitted on z4m's there (heavy cast iron block).
Here are some examples:
One completely destroyed/rubber squished to failure and the other one heavily worn/aged/compressed
https://www.zpost.com/forums/showthread.php?t=1606751&highlight=vibra
A pair in better state, but still 1 is distictively further squished and it looks like the rubber is getting squished from inbetween the plates. And it has little cracks in the rubber.
And these are pictures of unmounted mounts, so there isnt a huge weight resting on them now (if that happens, obvously they get squished more)
https://www.zpost.com/forums/showthread.php?t=1559609&highlight=vibra
So imho they do offer a distinct plus in that they give a better feel of a solid car in short corners, but I have my doubts that they'll have the same lifespan as oem ones.
That said, I had mine in there for 6 years now, which is roughly 35k miles, and are still reasonably OK I guess.
intake side:
exhaust side
The exhaust side carries more weight because of the slant six.
Sadly I have no pictures of how they are when dismounted; they are I guess a bit compressed compared to new, unmounted ones but I dont know how that changes when dismounted. Maybe I look into that in the future. The first pic I posted that one looks less squished, but that was when mounting, so 0 miles.
I guess its not a power issue (or better: torque issue as that determines the forces on the rubbers) because my engine makes more power than the /m and way more torque.
As far as heat goes, I have thinwalled stainless headers there which give off a lot of heat. But they are ceramically coated so I dont know if thats more insulating than a z4m header or not.