Male - 23 Years Old
Did someone really respond with Folie A Deux? Did that really happen? Anyway, agree with pretty much all your choices, Chris. The Billie Holiday album was released in 1958, so she'd only been making music for just over 10 years at that point. So that doesn't really fit into your 20 year rule ha. Fantastic album though.
Here's a few more late essentials:
B.B king - One Kind Favour
Al Green - Lay It Down
Miles Davis - The Man With The Horn
Leonard Cohen - Old Ideas
Etta James - The Dreamer
Paul McCartney - Memory Almost Full
New Order - Waiting For The Siren's Call
The Cure - 4:13 Dream
Bjork - Biophillia
The Bjork one is 'only' 18 years after her proper debut, so she technically shouldn't qualify under your 20 year criteria, but fuck it, she's been making music since the mid 70s so I included her. And it's a better answer than Folie A Deux.