Would anyone know the limiting age of Michelin tires (P275/35ZR-18 Pilot Sport PS2 ZP run flats)? I was told that my front tires are 8 years old (even though the tread is ok) and that their age was at a danger point. I bought them for my 2009 C6 Z06 and had them installed new in May of 2016. So, they were (unknowingly) 4 years old when I ordered them from TireRack. Drat - I was too much a newbie to check the dates when they arrived and were installed.