This piece in Shelf Awareness, Robert Gray: A Reader's Dilemma: To Resist, Finish, Adjourn or Abandon rounded up a bunch of different strategies.
The funniest? Librarian and author Nancy Pearl's "Revised 'Rule of 50'" that, Gray explains, was updated when Pearl was "In her 50s and 60s."
“I could no longer avoid the realization that, while the reading time remaining in my life was growing shorter, the world of books that I wanted to read was, if anything, growing larger.... When you are 51 years of age or older, subtract your age from 100, and the resulting number (which, of course, gets smaller every year) is the number of pages you should read before you can guiltlessly give up on a book. As the saying goes, 'Age has its privileges.' And the ultimate privilege of age, of course, is that when you turn 100, you are authorized (by the Rule of 50) to judge a book by its cover.”
The whole piece is fun... and interesting to consider. How far will you read before you decide to finish or not?
Illustrate, Translate, and Write On,