I used to work on some very intricate apparatus, which required only a very minute amount of lubrication oil, which was applied by a dampened brush.
So I suppose that the same applies to gyro bearings, they will need regular servicing, with a miniscule amount of lubrication.
Also each Gyro will have it's own inlet gauze filter which should not be blocked by dust.
Some of my friends worked at RAF Sealand as Instrument Technicians, but they would not even tell you if it was raining, in case they fell foul of the Official Secrets Act.