Homer: We were about to learn an iron law of show business: what goes up
must come down.
Lisa: What about Bob Hope? He's been consistently popular for over
fifty years.
Bart: So's Sinatra.
Homer: Well, anyway, we were all getting tired of --
Lisa: Dean Martin still packs 'em in.
Bart: Ditto Tom Jones.
Homer: Shut up!
-- Counterexample, schmounterexample,
"Homer's Barbershop Quartet"