Not that I know anything, but yes tire replacement timeframe is confusing. Rick at Parliament told me Prevo once recommended 10 yr replacement, then went to 7 once the heavier front axles, slides etc. were common. I also spoke to a Goodyear fleet rep who's thought was 20 years IF stored inside and with proper care. I won't risk that. May consider 10 if NO ISSUES apparent whatsoever. Then again, may replace steers sooner.