Hot Tap Water...Faster

A on demand water heater under the sink does the same thing. Insulating your pipes helps also. The more hot water you use the hotter the pipes get almost up to the water temp. When there is no longer flow, the water and pipes cool. Insulation will help but eventually it will cool to room temp. High pressure will get the hot water to the faucet only as fast as the water comes out of the faucet. (flow vs. pressure) You could have a closed loop system with a return back to the water heater and a circulation pump but that would continually use energy. Waiting for a gallon of cold water to clear out of a pipe is about as efficient as you can get.