This afternoon I ran the exercise prog a few times, adjusting the spring tensions on the pivot plates and greasing everything. There were a few rattles, which I eliminatd by making shims for the y-axis motor pivot plates.
After everything was moving smoothly, I use a laser-thermometer to check the stepper motors. here are the results:

Room temp: 71°F
Stepper temp: 138°F
Run time: 1 hour
Feed rate: 1140 IPM
Stepper size: 960 Oz/in NEMA34