The voice cast on "The Simpsons" are really getting up there

Harry Shearer is 69, Julie Kavner is 62, Dan Castellaneta and Nancy Cartwright are 55, Hank Azaria and Yeardley Smith are 48. Marcia Wallace, frequent guest star as Mrs. Krabappel, is 70! You can particularly hear the old lady coming out in Kavner's and Wallace's voices these days. How much longer can this show go on? They've had an amazing run with the original voice cast - would they ever replace one of them?

• So? It's their life's work and has made them rich and comfortable.

• They didn't replace Phil Hartman. All the characters he did were retired.