RE: Airplane long storage
Batteries is the hardest part to make them survive, NiCd maybe not, but I would be good to store them with some charge on them and place them in a cool dark place.
Nimh should be stored by the same method but fully charged. Lipos should be charged at its 80% ~ 90% and with the same characteristics.
Engines has been explained very accurate, in my personal experience, I fiil them (totally) with automatic transmission fluid and wrapped in plastic, trying to keep away any sign of moisture, using by a preference of mine a very old or unusable plug so the oil will not harm the element.
Good luck on your endeavor.
Alfred.