I got a pretty crappy interest rate (8.54%) on my loan even though I had a really high credit score. The problem was that I had insufficient credit history, this being my first big purchase. I've made 6 months worth of payments, paying ~15% more than my monthly payment each time. The current payoff amount is about $2000 less than what I originally financed. How much longer should I wait before I try to refinance?

I'm also considering paying a few extra thousand off the loan in the next couple months to help get a better refinance rate.