The only parts that generate friction in a brushless outrunner, is the shaft bearings. And unless they are very dry, in my experience applying lubricant doesn't really help. Easier to just change them out if they start to go bad (make noise). But if you do decide to lubricate them, make sure to use something rated for high temperatures.
That is an interesting question.
I would first consult your manufacturer's documentation. I didn't see any data at THIS website.
It may be that the motor was not designed for oiling maintenance though I cannot see how it would harm it unless a low quality lubricant is used and it 'gels'. Lubricants usually collect dust and dirt. A multi-copter creates quite a dust cloud at take off, much of which may simply get pulled back into the propwash/airstream until the bird is sufficiently high enough to escape the cloud.
If you have a high end competition type motor like Scorpion they address this issue.
Scorpion motors discusses this HERE.
THIS post has a citizen announcing motor service and subsequent discussion about repair and maintenance.
My personal experience with high speed motors is based on cost. Most industrial motors are made to be serviced. In the case of our hobby motors, if the motor is cheaper than bearing replacement, change the motor. Your motors are less than $15US. I wager that the bearings would cost more than the motor.
Then again you probably are asking if oiling the bearings will give longer life?
I have an RC hovercraft that was powered with a glow engine. The dust/grit in the environment it operated in slowly killed the motor. The RC fuels are self lubricating so I could have oiled every hour and it would not matter. In the case of that environment, I needed a air filtration system.