1518/1520/1717 Replacements

It always amazes me how I manage to overlook the most simple of things or just over complicate. Limiting throttle is a brilliant idea. I do remember BrianG saying somewhere that limiting throttle EPA to slow down your car isn't a good idea. What would be the difference between doing that (setting the throttle EPA to say 85-90%) and just not using the full throttle? I know what he said has to do with the FETs having the easiest time when they are operating at full throttle but not exactly sure about this.