Well, first a small hint:
Originally Posted by Radio and Electronics
Discussion of Radios, Receivers, Servos, Chargers, Speed controls, and More.
while
Originally Posted by R/C Tech Site Forum
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As for your question... as far as I can see, the MG90S is a tiny little micro servo and 2000-400 cycles per hour translates to about once per second. Non-stop over several days, if i understand correctly? My guess would be that it's just not made for this type of use. Does it have to be such a tiny unit?