No good test to prove you are free of Lyme exists to the best of my knowledge. Heck, the test to prove you have it isn't all that hot, accuracy-wise. Then you get ignorant docs saying it has too many "false positives", so there you go.
It looked to me that the new C6 Peptide test that Vetrinarians use to detect Lymes in animals in-house was the ticket, but it seems to have sort of petered out since it wasn't any more accurate %-wise than the standard W.B. test (though it supposedly detected the actual spirochete rather than the immune response to said spirochete). Even my doc who is pretty cutting-edge otherwise didn't know much about it, and wasn't terribly interested in learning more either.
Best bet is to keep track of any oddities/symptoms and periodically see your LLMD I guess.
I am sure there are some people who have been "cured" but some people have to deal with it the rest of their life. there are few studies on this, so I don't know the percentages.
My opinion - once you are symptom free, you need to keep your immune system strong, take supplements, eat healthy, and if your lucky it will stay in check. if you go back to unhealthy life style, eating junk, etc, it could take hold again.
any kind of trauma or illness can also make it come back in full force, such as accident, surgery, injury, pregnancy. these things are unfortunately not under our control, but we can remember to watch for signs of recurrent infection and any symptoms, including new or worse symptoms, and begin treatment right away. many people never even knew they had it until such an event.
From what I've read and doctors have told me once your body has produced the antibodies to fight Lyme, they will always show up. It's similar to mono and the EBV virus antibodies, once there present they will always be there. But after the bacteria or virus infection is under control, the antibodies aren't so abundant. In my case I had mono/ebv when I was a kid. My current Lyme condition has reactivated the mono/ebv virus.