I agree with billdozer, if the ball is performing well- use it, no matter the age.
What you may look for is how the ball goes through the pins. There is even some debate on that now with the modern equipment and rev rates. Either way, you will want to see a continued motion through the pins, with little deflection on the ball.
Ball recommendations, solid symmetric mid level performance with a controlled hook. Pick your poison from there. Maybe take a suggestion from the pro shop operator that will watch you throw a few. You wont need a top shelf ball with a lot of hook, or huge backend, IMO.