a biannually dismantle, clean and regrease with a good waterproof grease is all that's needed for swingarm rollers under normal riding conditions. annually if the bike is a regular racer is my take on this. headstem bearings and suspension fluids go with this regime.
Be careful to ensure the dust seals are in good nick and fit nicely. don't pack them full as a goog with grease as they may not fit back in the frame. ive played that game before.