How hot is too hot?

I've increased the voltage on the power supply feeding my NEMA 42
steppers to about 67 volts DC which is well under the 25 X voltage
limit. I've been warned that at too high a voltage the motors get
hot enough to fry eggs (a quantitative measurement, but one thats
hard for me to test without a pan.

After about 2 1/2 hours of locked rotor testing the motor is pretty
warm towards hot, but I can keep my hand on it without discomfort.

Should I be satisfied or concerned?

Regards,
Jeff