Learn perfect pitch in 15 years

So, I've got perfect pitch, and its not quite that black and white. For context, I can do all the regular perfect pitch superpowers (except for door rattles, which don't really rattle with a single tone), and have had it from a young age. When I first remember having it, I could only reliably recognise an A (and would have to count upwards to other notes), but unambiguously meet any definition as an adult

Many things that are considered perfect pitch skills take practice, and the OP is absolutely correct in that certain timbres are easier to classify than others. As a kid I would have had a harder time telling you the pitches if two woodwind instruments were playing a chord, vs two stringed instruments, due to familiarity. Its something you tend to work on accidentally as a background process as a musician

Much of perfect pitch discrimination is an active process though, eg being able to split up a song into its constituent parts and pick out the notes of each line is something you have to learn. All perfect pitch does is give you the ability to perform that discrimination, but anything more than that is a skill. For things that people consider to be perfect pitch skills (tone classification in a cluster), there absolutely are good days and bad days

Lots of pitches in nature aren't especially clean - nor are musical instruments, which is what makes them of varying ease to classify when you're unfamiliar. There are harmonics that can be make it hard to classify, or the central tone can be washed out in noise or similar tones. Its like trying to identify the dominant frequency in white noise, it takes practice

Its likely that OP had perfect pitch as a kid (demonstrating pitch classification), and simply never really capitalised on it mentally to develop it. Because you're right in that no adult has ever experimentally been demonstrated to have learnt this, even with extensive training and musical experience

Its worth noting that adults can learn something called pseudo absolute pitch, which sounds similar to what you're describing. The difference (which you're also describing) is that it requires reinforcement, and is a bit less accurate than having perfect pitch

Beato has a course for it. He says he used to have it but it has drifted over time. He also claims his young daughter has it now.

Uhh.... What? There's no guarantee that the song you hear ringing in your head after a certain time has passed is going to be in the original key, in fact there's a very good chance (depending on your range) that you'll end up subtly transposing it to a different key when you try singing it in the shower apropos of nothing.

This is by no means a guaranteed method to learn perfect pitch.

It should be noted that a lot of people mistake relative pitch for perfect pitch.

Perfect pitch means that I can sit down at a piano (or other instrument), play one random note, and you can instantly tell me what note that is. No preamble, no tuning yourself up, you can just do it.

Relative pitch is much more about recognizing intervals - a tritone versus a perfect fifth for example.

You'll find as was the case when synesthesia became the trendy fashion of the day that a lot of people like to believe that they possess perfect pitch when it's almost invariably relative pitch.