The line between my front two teeth doesn't line up with the line between my bottom two teeth. What can I do for this?

It is difficult to be specific without a picture of your smile. The question is "How far off are your midlines and which one is the one that is correct in your face?". The most ideal solution would be to go back into braces and line up your midlines. This may mean some compromises in other parts of your mouth. It may require tooth reshaping or removal. Veneers can be another alternative  but they can only accomplish so much. If the midlines are slightly off veneers are a quick fix. Tooth structure will need to be removed so that the lab has room to make the veneers. Veneers do fall off on occasion, usually when a patient is eating something they shouldn't be eating. They can be rebounded if this happens. How long veneers last depends on the patient. If you take excellent care of your teeth and follow instructions they can last many years.

at the end of braces treatment , facial - upper dental - lower dental  should be in one line. veneers need 1 mm preparation of front surface of teeth and little on back side. recementation of veneer is possible [ if not damaged]. after veneering, care is must. its difficult to say about longevity of veneer.