Age of "new" tires

Quick question for you guys - When you go to the local tire shop to get a new set mounted and balanced for your daily driver, how old would be too old for the new tires? For instance, if the new tires had a date code showing they were 3 years old, would you say something??? It happened to me over the weekend and I just noticed the date code now. I guess I should've looked sooner, but I'm curious what you guys think.
I'd take em back... Or ask em to prorate em! Whatever the % of 3 outta 7 is! Almost 50% What do they think? That they can just Pawn off their old stock, for full price?