I'm surprised there are 36 posts and nobody mentioned the
CIM Cooler. Check out some of their charts, they will show how much of a difference fans and heat sinks make. They will make a noticeable difference, and your robot safer.
You may want to check with AndyMark, but they may be able to deliver
http://www.andymark.com/product-p/am-2865.htm straight to your pit in STL.
For the last few years we have been running at least 2x 120mm fans on our drivetrain motors and I do believe they improve the long term quality of the motors.