I used comm drops for many years.. then decided is wasn't worth all the effort..
If you use comm drops on an off-road track, you will need to maintain your motor a bit more.. like clean it out every race. The comm drops have their advantage by helping the motor break in better, but they also attract dirt.. So unless you want to gamble with having the best power on a brushed motor every race, you really need to clean it out every race
.. don't forget to oil a bushing motor. Never spray out a bearing mod can or endbell with motor spray. The spray eats the grease and then you will need to oil the bearings all the time. The oil can get on the comm and cause you problems.