I know that members have 5 days to respond, otherwise the request times out and it goes to the next in line.

If that is the only copy then I am not sure what happens to wish list books. I have never had that happen.

I requested a book on the 12th, and at this time I am on day 3 of the second person, waiting for a response.  At least there are 11 copies in the system so eventually I hope I get it.

If they haven't accepted the request by the middle of the night on the 23rd, the transaction will be canceled and the book will go back on your wish list.

You go back to the number 1 spot.

If the person who posts the book cancels or doesn't accept the request you resume your spot at #1.  They have 5days to respond.  Some people don't check their accounts everyday. They may not have realized that they posted a WL book. 

This is probably an airhead question ,but how can you find out how many copies of a book are posted here?

Add the book that you are interested in to your reminder list. It tells you there, how many books there are.

Thanks.!!!