My service manual for the E450 V10 says that excessive idling is a special condition.
Under special conditions, the oil and filter needs to be changed every 3000 miles or every 3 months.
There are instructions written by Ford for long term storage. I haven't read them, but if your concerned, that would be the place to find out.
As far as gas or diesel, they are both internal combustion engines and not that different. The manufactures recommendations for storage are what should be followed, rather then opinions on a web site.
PS: After 6 months storage, all MH systems are fine.