Heat from Mamba Max esc

1.Two of my mamba max escs generate heat when throttle is at neutral.
Not much but enough to warm the heat sink to several degrees.
Any other esc has the same situation?
2.I run mamba max esc with neu 1515 1/y and 16.8v in my G3R.
Gearing is 20/66 and the temperature here is about 86 F .
The motor is warm but the esc becomes pretty hot easily around 122 F above.
I have a little Sunon fan on the esc and the wind blow is not much.
I did not push the truck hard; just 5 min. bash in the asphalt road.
Is it ok for the esc? Need I gear down when in grass field?
Do you have any recommendation or it is the time for mamba max monster esc.