A good regular clean and run the engine up to normal running temp at the weekends and keep it on the optimate. keep the tank as full as possible. If the bikes a minter keep it in the garage as Mr road salt loves Italian....
Don't know about dukes specifically (yet) but i always keep my bikes running in some way over winter. Even just warming up the engine at the weekend and running it up and down the drive to remove condensation from the bike helps i believe.
Give it a little polish or tighten/check a few nuts and bolts as it warms up. It all helps.
That and a complete going over with wd40 plus a battery charger.
It's 1000% better to keep moving parts lubricated by letting the engine and gearbox operate now and then or else you'll get potentially terminal problems IMHO. Engines will run practically forever if kept operational and therefore lubricated but if you let them stand for a while then that's asking for trouble.
And i agree about keeping a full tank too. Far less chance of condensation forming. I suppose you could add octane boosters if you're worried about fuel going "off" but perhaps someone can elaborate on this urban myth as i've certainly never had a problems starting a bike even after a few months with the same fuel in the tank.
My personal view is just leave it alone with petrol in. I do this and have never had a problem with all the bikes/lawn mowers/chain saws etc I have ever had. If its got carbs then definatelt drain them (or run the engine dry). IMO starting once a week is a bad idea (unless you are going to ride it) as nearly all engine wear happens on cold starts. Turning the engine a little every month would be a good idea to stop the belts getting a set. I do, however, always take it easy on the first Spring ride until the old petrol is burnt off.