The Michelins on my car seemed in very good shape when I bought my car - then one year later, on the highway, one of the rear tires lost a very large patch of its surface! It did not cause a blow-out, but I replaced all tires that day. Maybe it was from standing too long in one place, maybe it was from drying out, the age of the tires was unknown. My current tires (Pirellis) are now 6 years old and I think I will replace them in another two, three maximum, even though they will not be worn out then.
Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic