Synthetic oil questions

I just switched to Moble One last year on my 2011 Winnebago Using Fords oil In a years time I put 6,000 miles on it so I would change it in the summer then just before storage .I have done this for 5 years and did not change it this year with the Moble one oil. With my coach sitting in storage for almost 6 months a year what does time do to this oil. I will wait till I get 6,000 miles on it and change it . Once a year with the Ford filter would save me one oil change a year. As I do my own oil changes and wait till Costcos has there sale on 5w 30 oil would be around 40 dollars a year for me. I some times go up to 8,000 miles a year but from what I read in these post there would be no problem. If I was paying Camping World 140.00 dollars for one oil change I would go longer to off set these cost. Also the Ford book says when towing you should change the oil sooner. My coach goes no where with out our toad at 4,500 so would towing be a factor in these time of changing the oil. It is so true that growing up in the 60s and 70s the oil companys and the car dealers said 3 months or 3,000 which ever comes first . Old habits are hard to break.