How do you know if your overbite is fixed?

I have had my braces on for 1 year and 7 months and I really want them off. They said I can't get them off until November, but I would LOVE to be able to get them off before then. Here comes the problem: my teeth are perfectly straight with no gaps and have been for about 6 months now. All I have left to fix is my overbite. It was pretty bad, but I ALWAYS wear my rubberbands and have been for about 7 months. I am on the heavy kind with a box on left and a normal just 2 bracket attachment on right. Does anyone with EXPIERIENCE know about how much longer my overbite will take to fix?