What really bothers me about the Urethane products that we associate with our hobby, is that they should be good products. Urethane should have all of the properties we need to be used for motor mounts and steering couplings and such. I've seen Urethane used in a LOT of computer mechanical assemblies, some placed in more stressful environments than our cars would put the stuff. The trouble is, we used to work with the designers of the Urethane parts to ensure that they knew our environment and stresses involved and designed to it with a specific resin formula for our needs. I fear that the material we get for the VW crowd are parts cast using a stock, "one-of-ten-or-so" formulae used and what we get are parts that should be OK, depending on ambient temperature, oil or gas vapor in the environment, phase of the moon and position on the Mayan calendar.
OTOH, I'm using front beam bushings from Prothane (6+ years, now) and they're holding up very well. I had to drill them to accept grease fittings and shoot them with CV joint grease to keep them from squeaking, but that's about it.
The folks at Rhino seem to have taken the time to look at the stresses and environment involved in our motor mounts and tweaked their resin formula to make a product that actually performs as expected and lasts. Let's face it - the typical motor mounts in a VW sedan leave a LOT to be desired and were designed for about 40hp to the wheels, so coming up with a modern material that lasts for ten or so years, given the 3X+ HP we're torquing them with, is pretty damn good, in my book.
Still, given all that, I will STILL give them a close look (at least the one in the nose that I can actually see) every spring dust-off. You can't be too sure.