You need to keep them greased so the door opens and closes without a lot of effort. With that being said, keep an eye on the pin in case it wants to back out. My '37 uses a similar hinge setup and I use mirrors on both doors. The drivers top pin kept moving upwards till I rebuilt the hinges. I believe the loose hinges kept the door moving which worked the pin out. Since the rebuild, the pin has stayed in place, even with the grease.
