I have Michelin tires installed new in April 2013. Noticed this weekend that the left front tire is starting to show sun/weather cracks. Not sure why, as the MH doesn't sit parked for more than a coup...
Its been three years and being under an open covered facility does not protect from uv rays. UV rays bounce and UV radiation still happens on a cloudy day. You need covers for your tires, ones that allow air flow.