This morning I used a tote bag I haven't used in quite some time and found several postage stickers I printed from an APC in 2010!  If I can still use them, it's like found money - woohoo!

Can they still be used as valid postage?  If so, I now do printable postage (and love it - why did I wait so long?) - is there a way to combine these APC stickers with printable postage?

Yes Valerie, the APC postage should be good.  I doubt a zero strip is necessary.  Just use the face value and additional postage to make up any differences caused by rate increases. 

I have seen the PO cross out the old date and handwrite the correct date when they see these "OLD" postage stickers used on a package.

APC should be good regardless of date, it's the purchase date, not a postmark or mail date.  Hand written updates would be...lack of training?  How would they know if it was staff or customer, and what's the point?  When it's important (which APC isn't) they are supposed to add the zero meter strip, and it includes the 'official' updated date.

Thanks for the feedback.  On my next trip to the PO, I'll ask about the APC stickers just to be sure.

You might wish to use the UPSP website and ask their online experts.  Unfortunately, there's a lack of counter staff training regarding APCs...they frequently don't know much about that automated service.  Sadly, you're as likely to receive an incorrect answer as a correct answer.

they are suppose be like stamps but once i used an old apc stamp

and  my letter  got to the  delivery  post office only some clerk

ther crossed out the stamps and return the letter too

me with the notication 'stale' postage 

Incorrect by USPS Mark.  But unfortunately, many PO employees are unfamiliar with APC, even those with a unit in their branch are often undereducated as to it's proper use and limitations (or not).

I've had that happen too Mark. I dropped a package into a blue box picked up by the main PO, they wrote "stale meter" on it and sent it back. When it was returned I took it in to the branch office I bought the APC stamp at and asked them what the heck was up with a properly stamped package being sent back. They agreed it was perfectly fine and the manager went into the back to call the other PO and chew them out while one of the counter clerks crossed out their writing and sent the package on its way.