In general if the esc doesn't thermal the lack of speed in a brushless system will be the motor. If the motor gets hot the magnets lose strength and therefore power.
The RS Pro has more fet's than any competition esc on the market today. In an extremem situation such as the one you speak of we recomend the use of two of our RS caps as close to the esc as possible, with a small fan blowing onto the solder posts.
This is a picture of one of our Team Drivers Jason Moberly's TC5.