Proper motor maintenance is crucial to the performance and longevity. I say the rule of thumb is to clean your motor with “motor spray” every 2 race days unless you race outside on dusty tracks then it should be every race day. I sell motor spray here on my website. Be sure to spray into the motor and let everything drain out for 10 to 15 minutes. While the motor is drying, be sure to check all screws to make sure they are snug. Once the motor is dry, apply a couple drops of bearing oil on each bearing that is exposed. I recommend SHAG Oil.
I offer a bearing maintenance kit with all the essentials here: https://rotorron.com/product/rc-bearing-maintenance-3-piece-kit/