I don't think summer or not summer matters too much. Sure there will be more people on vacations during summer but that means your application might be slightly delayed, it will still be ahead of the ones that come in the fall.
If you change your address while your application is being processed, you need to contact the visa office and tell them. I do believe they prefer a real address over a PO box.
If you change your address while your application is being processed, you need to contact the visa office and tell them. I do believe they prefer a real address over a PO box.