If you are parked for several months there is a chance for that spot where the roller contacts the bearing raceway to begin corrosion. The storage environment dictates. Changes in temperatures may introduce moisture which leads to surface rust which leads to wear problems later. Proper lubrication is key, but if you store for several months at a time, an annual check is wise. An alternative is to store on frame blocks and spin wheels by hand a few times during storage. This keeps the bearing surfaces well coated and the load off the bearing rollers.