This tracks exactly with my experience. I'm in my 40s and my pitch is definitely no longer perfect -- it's close, though? It's not uncommon for me to be semiton

This tracks exactly with my experience. I'm in my 40s and my pitch is definitely no longer perfect -- it's close, though? It's not uncommon for me to be semitone off these days. Is this a studied aspect of perfect pitch? I've never read about it but, talking to friends, it seems like a common experience.