There's a bit of misinformation floating about in this thread!
It depends on how the paint has been stored, Spank is a fairly forgiving ball, often used by a rec sites etc., if it's been kept sealed at a consistent temperature and humidity it could well be OK.
Ask him if you can open up a box and inspect it, if the bags are sweaty or the balls misshaped then give it a miss, if you can open up a bag and drop test a few on to a hard surface, if they all break from a short distance then it is probably too brittle. If it bounces over next door's roof then its probably too tough.
I have shot year old Hellfire in December without any issues and a box of Midnight found in the back of the Garage that had been sitting on the cold concrete floor for over 2 years, that was a bit bouncy
Over boring on the barrel helps when you're not too sure on the quality of the paint.
Best bet is if you can try it out then negotiate a price with him, or if its beyond use, just say sorry, no thanks!