Hahaha, my CC1 that came original from my wife's car is also already 6+ years old and the tread are actually still quite thick! But got obvious cracks already and yes already hardened hence the already lousy grip tire becomes even lousier if that's even possible! So if really want to continue to use I think still can, just like what Continental said. (Michelin also provides warranty up to 6 yrs for their tires). However, having said so, I had previous experience with a Dunlop, which I use for almost 5 yrs before I changed them. You know what, the tires looked perfectly fine at a glance and they did perform fine right until that time BUT when they dismantle them from the rims, suddenly most of the sidewall rubber collapsed/came off the carcass, cracking all over! I was like shit, just a few weeks ago I still drove them to over 200kph, I suppose God still loves me after all eh! So yeah, even though tires might last that long, just be more cautious inspect them more carefully as they get old, especially if you drive long distances on highway speeds. use them at your own risk I suppose.

Agree, very overrated tire.

Dunlop Sport J5, better value for money.