My local tyre fitter won't sell tyres over 4 years old. He may perhaps fit them for someone if he didn't supply them, but would advise you on the age of the rubber, and would further advise caution depending on the vehicle they were being fitted to - but ultimately down to the punter.

I think, but may be wrong, that tyre shops consider tyres up to 2 years old from manufacture, as 'new'.