I was looking for anyone's thought on the longevity of the "coating". I see that some aftermarket companies offer 450cc kits that use an actual liner. Suzuki claims the coating dissipates heat better. Will the liner cause a heat problem? I am not planning on a 450 kit, but if the coating does wear off prematurely, I just want to know my options.

The coating should last a long time. It is what everyone has been using in their 2-stroke MX bikes for 15 years or more. Under normal use, it doesn't wear, the only way to damage it is to have a mechanical failure of some sort or to ingest a foreign object like dirt or sand into the motor.