The rubber in your ride’s bushings and mounts doesn’t last forever. Even in vehicles that don’t see a lot of miles, rubber will simply deteriorate due to age. The effect is gradual, so you may be riding on worn-out rubber mounts and not really feel it.
A failing mount or bushing will deliver a poor ride quality, with bumps and shocks becoming more apparent to the passengers. In extreme situations, the rubber will fail completely, leaving a metal-to-metal contact point. It’s important for both vehicle safety and handling performance to periodically inspect your rubber mounts and bushings for wear, and replace them as necessary.
This Summit Racing video, produced with help from the folks at Energy Suspension, explains why it might make sense to switch to polyurethane mounts and bushings. It demonstrates the difference between rubber and polyurethane, and lists some of the advantages of making the transition to a stiffer material.