How do you know when it is time to buy new balls? I have a cleaner and when they get dirty they clean up real nice. No chips. I think they are super aramith. I would think they last forever unless they chip off somehow.
I had a set of centennials for over 20 years. They still looked perfect and played great. I sold them for a very fair price, as they still looked new. The ONLY reason I sold them was that I bought a set of Arcos II and noticed that after MANY hours of play, there was not a single scuff or contact mark. They still looked perfect and didn't really even need to go in the ball cleaner! I had not realized that the Centennials were getting contact marks and needing more regular cleaning.
I don't honestly know if my Centennials ALWAYS needed more cleaning than any of the newer sets or if that is how they have always been and I just didn't notice it, but I did know they were the ONLY set I ever had that got little tiny white contact marks that became noticeable after a few hours of play. They came off VERY EASILY with a simple wipe with Aramith cleaner, but the new ball sets don't EVER get these marks.
FINAL NOTE: I love Centennials so I bought a brand new set. Assuming that over the last 20+ years the technology has much improved, and that Centennails are AT LEAST equal to Super Aramith Pro balls, I figured they should outlive me. The new ones play as well and stay as clean as ALL of my other new sets. I couldn't be more pleased.