As long as you take care of the equipment (cleaning, no drastic temperature changes, some surface prep every now and then), a bowling ball will keep its performance for a long while. In my club, many players toss around "old" stuff, and I am happy with my used balls, too (one of them has its 3rd drilling).
A new ball adds excitement, is like a little X-mas in the course of the year, but I'd rather see the necessity for something "new" when you want to fill a gap in your arsenal or if one ball is really damaged, e.g. big cracks, core separation etc.
IMHO, any ball can be brought back to good use. It is just a matter or rules (a minimum circumference must be guaranteed to keep the ball legal) and maybe place for plugs on the surface to keep a good track area.
I think everyone has personal preferrences about retiring or giving away old equipment. I could retire about 5 balls in my current arsenal, but I still keep them as fall-back options because I know what they do on the lanes, or as alternatives when the main arsenal is at the pro shop (what takes some weeks for me, since I have to take balls for surgery in a neighboring town at limited times...).
--------------------
DizzyFugu - Reporting from Germany
Team "X" website & more about me: http://web.mac.com/timlinked/iWeb/X/Thomas.html
"All that we see or seem, is but a dream within a dream..." - Edgar Allen Poe
