I used to print off a couple of stamps at a time (the more common postage amount) for future use when I would use the APC feature.   That way I figured I could potentially save myself from having to go inside the PO if the next requested book was the same price to mail.   I never had a problem, until I visited a different post office and the person at the counter made a comment about the date that I printed the stamp.   I think it was dated about 3 weeks earlier than that day.   She said that I shouldn't do that.  That any stamps printed using the APC should really be used the same day they are printed.  

Later, my husband and I were talking about it, and we didnt' get why I need to use it right away.   It's not like the price of the stamp is going to change over time.  If I bought a printed stamp for say, $2.41, it's still going to be worth that amount whenver I use it.   So any idea why she thought I need to use it the same day?

I believe with postage meters (company/privately owned) & the PO counter labels, the rule is in place for Accounting/Public relations reasons - putting something into the mail stream later than the date on the meter makes it appear that it took longer to deliver than it really did, giving the PO a poorer delivery time record.

In the case of APC's, I have heard that the date is meant to be a date of sale, not a date of mailing & you're allowed to do as you have done. The individual you spoke with is confusing APC postage with meters/PO counter labels. It can still be a PR problem for the PO as your recipient would assume the date you mailed the package was the date on the APC label & therefore it took 4 weeks to get to them.

Scott out.

I've only had this issue at post offices where there is no APC.  My feeling is that the date on the stamp is purchase date and that's all.

the date on the APC stamp is just the date you bought the stamp not the day you have to use it

Kellie, I've run into this as well.  This thread http://www.paperbackswap.com/forum/topic.php?t=120350 has a link to something on the USPS website that says you can buy APCs ahead of time and use them later. 

My post office said they just need to cancel the APC stamp on the date you mail it.

MY PO is actively tryign to get more people to use the APC, and they make a big deal about how you can buy multiple APC stamps and then post your packages later from home.