[Dafni]

Well, the more experienced RCer's can tell you more than I. But basically the cooler the better, ESC and Motor, of course.

The Neodymium magnets in our BL motors loose their strenght gradually when they get to hot. Depending on the grade of the alloy, they loose the magnetism above 120°C.

You can keep temps low with proper gearing, though.
This topic has been discussed many times. I remember a thread I made, called "questions on heat"