I do however take offense to the comments said by Volcanoadam... ear ageing??? My hearing is fantastic and I have the hearing of a late 20 year old, despite being in my 30's. Non-standard tunings? They're slightly annoying but you adjust.
I've heard that perfect pitch usually starts to degrade in your fifties (it's often off by a half step), and is often gone completely by the time you're 60 or so. I think this is what he was referring to. So if you're reliant completely on perfect pitch, you will have problems then. The same is true of pitch memory. Rick Beato made a video about Beethoven recently, and he mentioned that he used to be able to tune the low E of a guitar from memory, although he doesn't have perfect pitch, and it used to be dead on. But he lost that ability in his 50s.
The good thing about perfect pitch is that while you have perfect pitch - you also have (be default) brilliant relative pitch, so you can accept when pieces are in a different tuning system or in a lower tuning pitch.
I don't think this is true. I have perfect pitch and horrible relative pitch (just kidding

). But I don't think this is true. If you know that one note is a C, the next is a G, and calculate that the interval is a perfect fifth, that does not mean that you have relative pitch. Relative pitch is being able to think fundamentally in terms of ratios. Take music which just goes by so fast that you don't have time to think about the individual notes at all. Someone with perfect pitch will have to rely on their relative pitch, and if it's underdeveloped, will struggle with transcribing it (or at least I think so).
As for the adjusting to different tuning systems -- people with perfect pitch find it harder to sing in amateur choirs where the pitch keeps drifting. I think this depends a lot on the person. Some people with perfect pitch just find it grating when something is off pitch, and can't stand it, while others are fine with it.