While balls DO decrease in their performance characteristics over time, proper maintenance can extend their useful lives far beyond the 150-200 game range.
They may NOT fill the same place in your bag as when new, but many balls retain a good reaction profile after they begin to mellow out, and some become even MORE useful due to conditions we face at times, especially on the lighter side.
And, some balls CAN be brought back to life through techniques I have used that would be considered "outside" the accepted practices and only used as a last resort when there was nothing left to lose. I brought back a Track MUTANT from a point that I had never seen a ball reach. It was SO bad that my whitedot played the same line as it did.
IF a ball can reach the 200-225 game level, it could be good for one league for two years, or two leageus for one year ( 36weeks X 3games =108----108 X 2 =216 games ), just use something else for practice, maybe your old ball from last year.
Now, on the other hand, older technology balls last much longer. I've still got an old Track Coral Triton from 1997 that works great and has well over 1000 games on it, probably 2000 or more.
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"The difference between stupidity and genius is that genius has its limits."
Albert Einstein