This is just my recommendation for ball maintenance:
1: Clean after every set
2: Take back to OOB whether sanded or polished every 21 games
3: Oil extraction every 60 games
As an Ebonite/Hammer bowler this has not let me down.
If you have gotten 100-150 the first time(after oil extraction), and 100-150 the second time, you have no problem at all.
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"I don't want to be remembered, I want to be forgotten"