Yeah, if you are running roughly 20 miles with no loss of power, your batteries are OK. They may be on the downside of their life span but they are good.
It sounds like something is interfering with the throttle signal, or something that may be particular to that specific cart. That drain is minimal and should not noticeably affect the batteries.
If you would post the year etc. of the cart I may be able to help. Do you know if it has a factory or aftermarket 48 to 12 volt reducer?
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