[Al Skierkiewicz]

This is one of those problems that needs multiple solutions...
The armature dissipates most of the electrical losses in DC brushed motors and only connects thermally to the exterior through the end bearing surfaces and convection within the motor.
CIM motors have no way to cool the parts that get really hot. Even dropping these in cooling liquid will do little to remove that heat. The motors are generally intended for intermittent use, originally designed into trailer lift mechanisms.
The 550 and similar motors (like the previous FP motors), are designed to have some cooling air move through the motor from one end to another. Some designs will include a small but inefficient fan near the commutator to help move air. If you block the end where the mounting holes are located, no air will flow through the motor. Blowing air onto the motor frame with a small fan will help but it will not get cool air into all of the motor. Look carefully at the motor and be sure to keep all openings free to move air in your designs.
My recommendation is to practice for 30 minutes and cool down for at least 15. Use the 5 second finger test to determine the actual length of time needed. If you can keep your finger on the surface of the motor for at least 5 seconds, it is likely cool enough to continue. The robot is talking to you, you really just need to listen to what it is saying.