I had a book I'd requested go lost about a week ago, so that means it's now 5 weeks since I ordered it. It's a book that is available in the system, but only with about 2 copies available. I'm wondering how long I should wait before I give up on the lost book ever arriving, and just re-order it from someone else. Is two months enough? Any thoughts?

Hi Loretta.  This is what the Help Center says:

If a book you requested does not arrive by the 26th day (the 35th day if the sender or requestor is outside the contiguous US) after it was marked mailed, it will be declared lost in the mail at PBS. The requestor does not mark the book Lost; the system does this. 

The requestor will get credit back, and the book will go onto the Wish List (if there are no available copies in the system) or the Reminder List (if there are other copies available to request).  If the book was a Wish List book when it was requested before, the requestor will go back to his or her previous place "in line" for the book.

• However, this does not mean that the book is definitely lost.  Sometimes it is merely delayed en route.
• If the book arrives after it has been declared Lost, the requestor must mark it received from the Transaction Archive.
  • At this time, the credit will be taken back and given to the sender for sending the book.
  •  

What you should do if a book you requested is declared Lost in the Mail:

• Contact the sender, to find out if mailing was delayed for some reason.
  • you can do this from your Transaction Archive, using the PM button on this Lost transaction in that list.

• If the mailing was not delayed, the sender should call 800-ASK-USPS or go to http://postalinspectors.uspis.gov/forms/MLNtRcvd.aspx (the Postal Inspection Service's website) and input the information online there . This will help USPS try to recover the book if it truly has been lost in the mail.
• Don't re-request the book for at least 2 weeks, unless you are willing to run the risk of getting two copies (and paying a credit for both).

I would wait another week and then re-order. At least you know it isn't a heavily posted book so you probably won't have a terribly long wait when you relist it or if you get a second copy. A lot of times books go "Lost" because the sender has not mailed it when they said they did, in which case you will get two books but if the person you first requested the book from did not send it until within the week it is declared lost you DO NOT have to give the first sender credit. From the Help Center:

• If the book was declared lost in the mail and you requested and received (or will receive) a second copy because you thought the first one was really lost:
  • If the postmark was from the week before the book was declared lost (or later!), and you got no notification from the sender that the book would be/was mailed late: you do not have to mark this book received (this is the ONE case in which you don't have to mark a received book received: if a very late mailer without notice caused you to reorder the book and end up with two copies).  
  • OR: You can mark it received to note the late postmark, and ask for your credit back in your Personal Message to the sender.  If you don't hear back/don't get the credit back within 3 days you should contact us using the Feedback link at the top of the Contact Us page.
  • You can also note this information about the late mailing in the Comments box at the bottom of the Book Received page, while marking the book received: this will go onto the sender's record.

It sucks waiting the two weeks, especially when the person never reads their PMs or anything. I'm just now able to safely reorder a book today that went lost two weeks ago. They've never read my PM about asking if they forgot to mail it or anything. Obviously they didn't, or I'd think they'd answer their PMs.

This has happened to two books here lately, and I'm just a couple days from getting that first PBS email asking if I've yet received the second copy of the first book (different from the one I mentioned above) that I had go lost. Seriously, all three of these books were/is from people who use DC. I can't believe I have such bad luck that all three people would pay for it then drop the ball when it comes to sticking the book in the mail. I guess we all hit a rough patch eventually, huh? Update: The book just now got a scan on it so my reorder of the first book is successful so far.

So yeah, basically I'm saying wait the full two weeks to reorder. I know I don't want to give these people a credit on the off chance their book does show up eventually, so I assume you might feel the same. I get that it's not their fault if they did indeed mail them (which I'm seriously doubting at this point) but they could at least respond to my PM and say if they mailed it. I kind of wish PBS would rewrite the Help Docs and say if the person doesn't respond within a week, like with an RWAP where they're required to respond, that you can go ahead and reorder instead of having to wait the full two weeks after a book goes lost.