Two prolific writers from two different centuries agree: 10 pages a day keeps… uh, “not being prolific” away.

All those I think who have lived as literary men,—working daily as literary labourers,—will agree with me that three hours a day will produce as much as a man ought to write. But then he should so have trained himself that he shall be able to work continuously during those three hours,—so have tutored his mind that it shall not be necessary for him to sit nibbling his pen, and gazing at the wall before him, till he shall have found the words with which he wants to express his ideas. It had at this time become my custom,—and it still is my custom, though of late I have become a little lenient to myself,—to write with my watch before me, and to require from myself 250 words every quarter of an hour. I have found that the 250 words have been forthcoming as regularly as my watch went. But my three hours were not devoted entirely to writing. I always began my task by reading the work of the day before, an operation which would take me half an hour, and which consisted chiefly in weighing with my ear the sound of the words and phrases. […] This division of time allowed me to produce over ten pages of an ordinary novel volume a day, and if kept up through ten months, would have given as its results three novels of three volumes each in the year;—the precise amount which so greatly acerbated the publisher in Paternoster Row, and which must at any rate be felt to be quite as much as the novel-readers of the world can want from the hands of one man.

— Anthony Trollope, An Autobiography, ch. 15


I like to get ten pages a day, which amounts to 2,000 words. […] On some days those ten pages come easily; I’m up and out and doing errands by eleven-thirty in the morning, perky as a rat in liverwurst. More frequently, as I grow older, I find myself eating lunch at my desk and finishing the day’s work around one-thirty in the afternoon. Sometimes, when the words come hard, I’m still fiddling around at teatime. Either way is fine with me, but only under dire circumstances do I allow myself to shut down before I get my 2,000 words.

— Stephen King, On Writing (section 2 of “On Writing”)