Georg Diez has a good piece in Der Spiegel about writers who need to think about calling it quits. Diez takes note of the American novelist Philip Roth's decision to stop writing books and believes that a number of other writers should follow Roth's example.
Specifically, Diez mentions Günter Grass (in particular, Grass needs to stop writing bad poetry), Martin Walser, Uwe Tellkamp, and Martin Mosebach.
In truth, very few wrtiers can sustain greatness over a long career. The number of writers who we wish had written more (Wolfgang Koeppen comes to mind, or perhaps Werner Bräunig) is far outweighed by writers whose creative powers diminish over time but persist in putting out book after book (Christa Wolf is just one example). Exceptions to this literary phenomenon are few and far between (Thomas Mann, to be sure, or Philip Roth's late rival John Updike).
Whom would you add to Diez's list?
I would immediately add Elfriede Jelinek (we get it already: men are sadists, America is evil, and Austria belongs to the seventh circle of Hell.
On the non-fiction side I can think of any number of writers who should stop: Thilo Sarrazin had his 15 minutes of fame and can stop writing books. Eva Herman and Udo Ulfkotte never should have picked up a pen to begin with.
Which American writers should follow Roth's advice? The list is endless: Tom Wolfe, T. C. Boyle, Barbara Kingsolver, etc