There is usually a use or freeze by date on the package. Go by that date.
BTW, is price that for spares or baby backs?
Still a good price. (I'm jealous)For BB's that would be a steal.
If they're in a cryopak you can usually hold for a longer time.(check the dates)If they are living in a foam tray, who knows.The cryo date is set by the packer.Once the store breaks them into foam traysthe real date can go out the window.
I was going to be a wise ass and say I can hold them pretty long if they aren't too hot.Glad they are still good, and good luck with your cook!