I'm in the same boat. Mine is 1988 stuff and though well maintained, it cant last much longer. It's also not very energy efficient compared to more modern units.
The heat portion of it was replaced about 1995 and works fine. The rest is the origional still. Looking about, the life cycle of this type of unit, was for 15 years so we are on borrowed time <grin>.
And Steve explianed I used the wrong term. Sorry, it's refridgerant. Apparently still in production but all I can say is I get warned each time that mine is getting hard to obtain in my area. This from repair guys, not ones who make money selling new systems. There are also parts issues with my older unit but so far they have been able to get what is needed.
The AC unit is one of the things my husband deals with so I'm not totally up on it.
Waiting patiently and hoping for good news! With your unit being only 12 years old, you may be lucky like me and be able to keep it running another 8 or more. If it helps any, ours is an upper end Sears unit and as part of the purchase contract had annual maintenance for the first 10 years I believe. Unfortunately that didnt transfer to us when we bought the house so we've had to use various contractors.
We don't know if it had refridgerant added while we were away overseas, but we had it done once when when we bought the house and again about 6 years later just before we left. That would mean if it doesnt cool well this year, it's time for another addition most likely (will have been 7 years).