When will my PTO postcard arrive?

Dear Rich: Last week I mailed an application for a Provisional Patent to the USPTO. I sent it via Express Mail on and enclosed a stamped, self-addressed postcard. It's ten days later and I am wondering how long it should take, on average, to receive confirmation of their receipt of the application via that postcard. BTW, should the postcard never arrive, are there other ways I can confirm that the application was in fact received by the USPTO. According to Patent it Yourself author David Pressman, you should get the postcard from the USPTO after about two weeks. You should also receive an official filing receipt from the USPTO after about a month. Of course, you can always verify whether the USPTO received your item by checking the Express Mail records online or checking with your credit card company or bank to see if the payment went through. If you never receive the filing receipt, or there is some other discrepancy, call the OIPE (Office of Initial Patent Exam) at 800-786-9199 or 571-272-4000. If the OIPE doesn't have a record and if you mailed it by Express Mail, the Dear Rich Staff notes that you can avail yourself of the remedies under Rule 1.10 of the Manual of Patent Examining Procedure.
In the future. Pressman, like many patent practitioners, has embraced the electronic filing system (EFS-Web) He recommends that in the future you consider filing electronically, because that way you get an instant filing receipt and serial number. (And if you're a registered efiler you can also instantly view the application details on the USPTO's Private PAIR site.)  
Speaking of patents and mailing ... Isn't this 1969 patent (above) for mailing vinyl singles the cutest thing?