I've come to appreciate when artists hang it up in their prime, though. It's very hard to be consistently good forever (I'm not sure I can name anyone who was), and I would much rather think back on an artist's work and say "man I wish he did more of that" than "man he should've gave it up ages ago". For example, Calvin and Hobbes vs Garfield in the world of comics. I would love to have more C&H of the same quality, but I'm grateful it never became boring and forgettable like Garfield did.
George Harrison tried his best at producing, but he just didn’t have it. Doris Troy’s album under Apple has very little soul.
Too bad John and Paul didn’t care enough to consistently produce other artists.