Tyres- What age would you change tyre(s) at? AND....120 section on the front?

[acid drop]

Cracking is only one problem with old tyres, the other is that they harden, thus less grip especial in the damp or wet or cold roads
I would change them  5 years and over.

Check the date stamp  as already mentioned

  Change them at five years???  mine don't last more than 18 months