Tire lifetime must depend on factors unknown.
My motorhome tires cracked and had to be replaced at age 6 years with plenty of tread left. Of the four ten year old tires on my old van, two had some small sidewall cracks so I replaced them last summer. The other two looked fine so I ran them another year. Replaced at age 11 years when my daughter was going on a trip with the van, and some tiny equally spaced x cracks appeared around one sidewall. All Michelin, no covers ever used. I have an older van that has been parked in the yard for 20 years - no flats. I think I aired them up about 5 years ago. My daughter's very lightly driven Caravan had tires deflate through cracked sidewalks at age 4 years.
I use covers on the motorhome's year old Michelin MS2s.
2004 E350 Adventurer (Canadian) 20 footer - Alberta, Canada
No TV + 100W solar = no generator needed