I change my oil every 5000 miles, but thats as much as I put on it in a season anyway. So for me, I change it every Spring. I know I always mention this, but its worth repeating. The overhead cams in the V-10 don't have any bearing shells, they run right in their journals. So if you get wear or slop in the valve train the only remedy is new heads. Your only defense is frequent oil changes. You want the valve train to last at least as long as the rings so you get the full useful life out of your engine.
Retired Anesthetist. Pilot with mechanic/inspection ratings.1996 Jayco C 22 foot with 460/Banks Powerpak/Bilsteins.Wife and daughter. Two cats which control my life. 1975 Ford F-250, 84 Coupe Deville, Thorp T18, tons of tools and tons of junk.
As mentioned...oil won't break down in a relatively short period of time, and since just about everyone agrees that they would change their oil in 2-years or less, there isn't a problem. Of course, as was also mentioned, moisture in the oil IS a problem, and you should get the oil up to operating temperature to burn it off.
I've seen a diesel engine that had a blown head gasket, with oil that looked like a mocha coffee...that much water in the oil! After we replaced the head & gasket, and then ran it for a couple of hours, the oil looked like new. Probably not recommended in a car, truck, or RV engine, but on tugs, where there is 190 gallons of oil in the sump, you "run" the water out of them!
It's worth it to take the RV out for a half-hour drive...the $20/month will do a variety of beneficial things for the engine, transmission, and drive train, as well as the brakes, tires, etc. Plus you get to drive the rig...how cool is that?
I agree that we should follow the recommended numbers. Though I'd probably go for a seasonal change, if I didn't travel enough to reach the numbers the manual suggests. With the synthetics, you will be allowed greater times between changes, but I'd still keep things under the 2-year window.
JMHO
Bill, Claudia, and the Paps
DH Bill / DW Claudia / DD Jenn / DS Chris The Paps! Sophie, Abby, Brandy, Kahlie and Annie
2000 Winnebago "Minnie" 31C, Ford V-10
Purchased April Fools Day, 2008 The Pets
To think that you need to change oil by date rather than mileage as recomended by the oil change people is stupid! According to them 3000 miles or 3 months on oil is time to change. Good policy to improve business. During my working career I drove at least 22 different company cars and our program was always 6000 miles between changes without regards to time. Never had an oil related problem. On my M/H I do a 6000 mile change and have yet to have any problems.
A interesting link to read about oil stabilisers is www.trubluoil.co.uk - then from side bar click products and stabilisers ,their video is also interesting.I own a number of high performance vehicles and if you took any one of them with 2000 miles on the oil and blindfolded me and had me start it a number of times with either the old oil or fresh oil I guarantee that I could tell you which time I started it with fresh oil---it all has to do with viscosity breakdown from heat and also from "cheap oil" . Amsoil has alot of details and graphs of their testing different brands for viscosity breakdown and the ability not to shear in roller bearing applications
A local Ford dealer's RV service manager told me to change oil every 6 months as I haven't been putting enough miles on it to follow the mileage oriented oil/filter change schedule. He advised me to keep receipts and keep a record of changes by date as backup to potential warratnty issues.
Why are you starting it once a week? Don't start it to charge batteries. You can just plug in to charge batteries.
I would just start it for the actual trips.
I am from the old school and change the oil in my motorhome's 2007 Ford E350-V10, every 3000 miles, using the cheapest SAE approved 5W-20 oil, and the cheapest oil filter. When I say cheap, I don't mean inferior, I mean what's on-sale. I don't like to use those super-filtering oil filters as I am fearful of oil restriction upon extremely high rpm conditions.....like engine braking down a mountain.
Oil will get dirty, so I think it's best to flush out the dirt sooner than later.
Adding here I change my own oil too. Yes while on vacation.
Given our RV is kept indoors when not in-use, there is much less an issue of duration in time, so I use miles only as my indicator to when it needs changing.
Off season, I keep the RV plugged in to the house, but never start the main engine or the generator. This is my first full year owning a generator....I'll see how that worked out next month.
Bought new in June 2007, Phoenix Cruiser-2350
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After we replaced the head & gasket, and then ran it for a couple of hours, the oil looked like new. Probably not recommended in a car, truck, or RV engine, but on tugs, where there is 190 gallons of oil in the sump, you "run" the water out of them! 
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