it depends on the specialty. If you are applying for ophtho, you really don't have much choice since programs have only two interview dates and interview dates are usually the same. This forces you to choose between programs and skip some.
But if you are applying to radiology for example, which tends to have more interview dates, then the ans. to your que. "it doesn't matter when you interview"
Usually, the applicants are scored right after their interview by a number system. So even if you send thank yous etc, it really doesn't make a difference. However, if the program is your top choice and you interviewed there early in the fall, I would definitely revisit or contact the PD before match time letting them know about your interest in the program (esp. if you have not done an away at that place). This can help you in the rank list ONLY if you are a competitive candidate to begin with.