The motors don't require cooling.

Dual or tri-cell gets a little warm only.
My personal experience is that even pushing Lego wheels with a dual cell on carpet barely warms up the motors I've tried, so I don't know where this motor cooling junk is coming from.

Don't let hype replace facts.

As an appearance thing, if it's done right it looks okay, but don't for one minute get yourselves all wrapped up in a non-existant motor cooling issue.

If everyone would take a few minutes to actually test the situation to see how much heat ISN'T being generated, then we wouldn't get HALF of this "hot motor" nonsense.