You should file all applicable extensions if you can.
While you may not need the extension if you are due a refund, you lose the right to make most elections on your return when you late file if you didn't file an extension by the regular due date, or you still don't file by the extended due date. Some states also impose minimum late-filing penalties regardless of tax amount due (ex: minimum $50/month), so filing the extensions could still save you penalties.
