Can we dip a toe in other genres?
I'd say Thelonious Monk had a pretty stellar run from '51 to '68, and was especially proficient from about 1955 to '67 (the Orin Keepnews recordings through to Straight No Chaser).
Glenn Gould cuts it close, he peaked in '55, was done performing by '64, but put out great stuff through '67. 1969's The Latecomers is good, but not great...
I've been on a huge Sinatra kick lately (when I was growing up, my dad was a big fan and maybe I'm just hitting that age). But, when you've loved and lost like Frank has you can put out a solid string of great albums. His work from '45 to 1960 is great, beating the 10 year rule by half-a-decade.
And while on the topic of Frank, is there a better nickname than "Chairman of the Board" - seriously? maybe "the Baby Faced Assasin" but that's about it. And I freakin' love this quote from Ava Gardner's recent bio: when she asked what she saw in the 119 pound has been, Gardner replied that 19 pounds of Sinatra was cock.