To be fair, we have done some 20+ POD's and only 1 or 2 have missed the 2 week mark. Most come in before then. Jason's probelm was a big one I admit and might have jaded everyone involved on the process of pre-announcing.
My general opion and based on feedback/complains of users, is that 1 week ok is ok. More then that is a pain. Less then that is best if you can wait on the release. Or in the case of RPGObjects he doesn't even bother to co-release them anymore.
I really comes down to TELLING the customer what to expect. If you plan to release a POD within a week after the PDF, tell them. If you plan to release the POD at the same time as the PDF and don't really have the POD in stock at the moement, TELL THEM in the description the expected ship date. They get the PDF to review while they wait and it's usually never a problem.
So, it's your call till I get more data on the whole subject. But those are my thoughts.
Oh, and I think I'll have your book in time for GenCon
James