Tyre Age When To Replace?

On a bike you should not ride tyres which are older than 5 years!!!
It is dangerous. You play with your life when you use older ones. They may look fine, but the grip changes and you can not trust on their behavior on different kind of street surfaces!
You should spend the additional money for new tyres after your bike decision!

 

Change them - they’ll be rock hard (comparatively speaking) now and offer limited grip

 

My ZZR, which now covers very few miles, has front and rear tyres marked 3420 and 3320 which will make them 5 years old around August this year. The front was fitted in March 21 and is about 2/3 worn but the rear was fitted much later, possibly late 2022, was one of the last Pilot Road 2CT's available has done around 1000m. I'll probably change the front this year and and keep the rear. How and where the bike is stored can affect tyre life . Kept outside in extremes of temperature and weather accelerates ageing.
A bit of googling brings up an industry standard life of 6 years from DOM which can be extended a little with correct storage.
Tyres 11 and 12 years old are definitely out.