It is best to change oil before storage. Would I change the oil if it was changed recently, like 500 miles before? Probably not unless the 500 miles is all short trips. You want to avoid storing the bike with contaminents in the oil.
Here is a good thread on storage:
http://www.ducatimonsterforum.org/index.php?topic=4169.0Good link.
Here is my short version:
0. Wash bike first! A cold wash is fine, just get all the grime and spill off.
1. Add Stabil to a full tank. I use the stabil marine and triple the amount. Run the tank down to at least half.
2. Park the bike, lift tank and turn off the fuel feed on carbie models.
3. When still warm, drain the oil. Let it all run out, and let it sit overnight. This will get a lot of the moisture in the engine out as well as it condenses when its cooling.
4. The next day, add new oil and filter. Remove spark plugs. Open the air box and expose the intakes for the throttle bodies or carbs. Give them a spray with fogging oil while you crank the engine. Keep the switch to OFF so the engine just turns on carb models and make sure the spark plug caps are covered so they don't ground on the engine. You really just want to spray enough so it gets to the back side of the valves and oil pressure gets up to turn off the light (to distribute the new oil).
5. Spray a few spritzes in the spark plug holes. Put the bike in 1st gear and turn the engine by rolling the rear wheel (the correct direction!). It's easier if you have it up on a paddock stand.
6. I leave my battery on the bike and put it on a tender.
7. Last, I use the S100 anti corrosion spray on exposed metal bits.
8. Rotate the engine every few weeks to keep the belts from "setting", and move the bike if the tires on the pavement.
That's all I do and it works well.
