Especially running outdoor, you will be surprised how much "dirt" is inside the motor, once you take it apart, especially the motors we use in 1/10 TC's that have very large venting holes in the can.

Also, the oiling of the bearings, if you do it while the motor is assembled, and you just want to apply a drop of oil in the front bearing, be sure you have cleaned it as much as you can, otherwise you will only get dirt in the bearing with the oil and that will significantly reduce the life of the bearing.