I agree with all of that BUT polygraphite will last past your life expectancy. They don't degrade like rubber and they are are harder than a hockey puck. Our cars flex all the time anyway due to the nature of the unibody. Polygraphite mounts are darn near solid so don't get nervous if you have them with subframe connectors, they are very compatible. Keep in mind that connectors are more for horizontal movement not lateral. Body mounts contol lateral movement. You can mix and match depending on how much lateral movement you want.
Jim