I came home from a long trip in October 2014 and changed the engine oil(synthetic) It has sat other than local trips to and from storage and to get maintenance. I have started it up every month or two...
My question and opinion Cost of Rig Cost of Oil change (every year as recommended by manufacture) Cost of piece of mind.
Me I change every year, if I happen to drive near 900 gallons of fuel burn, in less then a year. I will change it. Even if it means twice in 1 year. Small price to pay for piece of mind and ensuring I do not hurt my Rv.