Done with game
None of the gym leaders rebattle you in Pokemon white. The only time they battle you is the first time when you get the badge.
You can't rematch a Gym Leader, except for HG/SS, and, I think just Platinum, where you can find them in the Survival Area (Platinum) or the Fighting Dojo (After obtaining their phone numbers and finding the Karate King).
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The points system
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