Servo Operating Temperature?

I finally have my mill converted to servo control and am just
wondering how hot servos generally run. After being run for about 1-
1.5 hours the Z axis motor is slighly hot. You can still keep your
hand on it no problem but it is a little hot. I didnt get a chance
to run it any longer than this yet.

They do have a sticker stating to use caution when touching them
because they can get hot, but i'm just wondering how hot is too hot?

The setup is Electro Craft E-543 servos running off G340 drives. The
gain/dampening knobs are just left at factory settings. Current
limit is set at about half, thats all the torque I need. Thanks in
advance.

Mark