Can I pre-print postage from the APC (I was thinking of printing a few 1 lb MM rate stickers) and then use it weeks or months later?  I thought that a package with APC postage had to be mailed the same day the postage was printed. 

Go for it Jennifer, many PBS members report using this method.  APC is considered more like a postage stamp, and the date doesn't matter.

yes  you can but some post office (espeecilay ones that do not have  will tell you it had been mailed on the day you printed it]\

of course they are wrong,

i once had some mail retruned to me -because antoher mailing center thought the apc stamp was stale

even thought i had handled to a postal clerk in my local post office

I do that all the time. BUT, the one time I accidentally put it into a bluebox  the main branch picked up instead of the substation, those knotheads sent it back as stale postage. I took it into the substation and they added a zero-strip to resend it and called the main branch and chewed some arse.

The moral is - APC stamps are just that stamps. They have a purchased on date, they do not have a post mark on them. They can be used whenever, just like any other stamp. But some post offices don't know them and don't understand them so they don't handle them correctly. I would recommend only doing it for one or two to see how your post office handles them before sending out too many with older purchase dates on them.