The industry class tyres made in the last 2 years as new. I guess it depends how long you expect them to be on the car as they will harden in time. I was offered some 2012 tyres recently but declined as they might end up being 6+ years old if they last 3 summers.
I'm running with tyres from 2005 in my AC
Not ideal but they are OK ish
These tyres have been mounted in the car and it has been garaged most of the time but I do notice the car slips easily under acceleration sometimes, but that can also be related to 400 ponies hitting the rear wheels on short notice
ROSPA and others provide some guidance about this. 'Tyres that have been in storage should not be placed into use if they are over 6 years old, from their date of manufacture. When a tyre has been in use, the effects of ageing are lessened to a degree, but such tyres should be replaced after 10 years.'
The tyres on my car when I bought it must have been from old stock purchased by previous owner.
He did mention TireRack in the US as a cheap source. I was advised by the local Pirelli guy they were up to 7 years old manufacture.
The new tyres PZero transformed the car, softer riding and grip able to transmit the power without skating and squirming.
Really improved the performance.
Don't go old.
Old tyres may look ok, and perform ok under easy conditions. I have 7 year old Goodyears on the Alfa , it came with them, loads of tread, however, I took it for a "spirited" drive hard cornering etc. and now have a nice full circumference crack on each around the blocks.( A new set was on the cards anyway.) Don't scrimp on tyres it's the only thing between you and the road, and a small area at that.