First of all, as most people have replied, I do agree, why change it if that's not why you bought the ball?
2. If you have a spinner, it's very easy to go back and forth. I just wouldn't do it too many times.
3. As to polish or a finer coat, it all depends. I use both. I'd start off with 2000 Abralon first, then 4000 Abralon. If polish is still shown to be needed, then I'd take the cover to around 800 grit US and adda light coat of polish, like Valentino's Snake Oil.
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"None are so blind as those who will not see."