Sampas, Connors and Ashe never won a major after age 31.
Agassi's won his last major at age 32.
John McEnroe
John won his last major at age 25 in 1984 and after that never again.
of course it is normal that players decline and in the 80s players did probably have less longevity than now because of a less professional lifestyle and more matches played.
but still many guys won majors at least till they were 27-28 or so (lendl, connors) so why couldn't mac win a major from 26-28?
did he decline earlier due to injuries or something? or did other players just overtake him?
Bjorn Borg
Retired at age 26.