New tires in three years, you cannot be serious???
While fresh tires would have been nice, I might take one year off for the two years in storage. I went seven years on my front tires and 10 on the rear as I put almost all of the miles on them with proper inflation and care. The best thing you can do for your tires is to use the MH often as sitting in one spot for many months is why some say 5-7 years.
PS: I put my 10 year old tires on my dump truck as they were better (Virgin) than the recaps on the rear. Granted a blowout there will not hurt much.
OP since you are in VT forget all of the above and replace them in three years as my brother lives in NH and he will buy them for $100 each. :WGuess what he'll do with them... Yes he owns several dump trucks.
