I had "temporarily perfect" pitch when I was younger, especially when I was regularly playing the cello. I could pick up my cello and tune it without a reference, and I could recognize a note or key that was being played. I kind of took it for granted.

Then one year my family went on a long car trip for a few weeks -- without the cello or even a radio since our car didn't have one -- and when we came home, my pitch was gone. It took just a few days to get back, but I realize that I have some sort of short term memory for pitch but do not have perfect pitch. It's not something that I'm concerned about practicing or maintaining. I'm a jazz bassist today, and my pitch is good enough for picking things up by ear, and maintaining my intonation while playing.

I wonder if there's a "spectrum" of pitch ability, and also a spectrum of how readily different people can learn it.