I'm not thinking about Ice Dance for the moment, because in the past mostly when one Ice Dance pair was champion, they remained champions until their retirement from ISU competitions.
John Curry won in 1976, Euros, Worlds and Olympics.
Katarina Witt did it in 1988.
Didn't Albright and Heiss win Worlds after their Olympic wins?
Yamaguchi did it in '92.
I'm sure there are more skaters, but this is all that comes to mind right now.