The pinion on my trugs have been on for 6-8mos w/o indecent or loosening. Get good blue locktite, torque down w/ a good wrench, let cure 24hrs and you should be set.

I have very inexpensive hi-torque hex keys from McMaster Carr. (EG item # 6625A62, <$4.) Better than any hudy or Ae or other $$ rc hex wrenches I've used. You can crank the S out of the hexes w/o stripping. As the edges of the hex keys wear down, trim down w/ a dremel a few mm and its good as new.

Use red if you never ever want to remove the pinion from the motor shaft (w.o using a blowtorch, etc)