[Al Skierkiewicz]

I have to add to Joe's statement about Freeze spray is that some products contain other chemicals that can wash lubricants out of bearings. Use with caution. Remember that the majority of the heat generation takes place in the windings that are mainly coupled to the outside of the motor through radiation/convection within the motor. There is very little air movement inside a closed motor. The only real connection to the body is through the bearings and brushes.
The effects of heat in addition to those above is the possible breakdown of the insulating varnish on the windings (eventually leads to failure), the change in efficiency of the magnetic structures in the armature and the expansion of metal parts inside and outside the motor.
If the motors were hot (could not pass the five second finger rule) and the battery wires were hot as well, this is a good sign that you are using a lot of current. You should consider a cooling scheme for the robot in between matches. High CFM fans come to mind.