It is easy to confuse length with profundity, brevity with shallowness. The reverse can also be true, of course, but readers frequently believe that an epic-length novel must have some kind of importance, even if it does not always justify its length.
Milan Kundera (The Unbearable Lightness of Being, 320 pages, give or take) noted this in an interview with The Paris Review. He praised Robert Musil’s gargantuan yet still somehow unfinished multi-volume novel about the end of the Austro-Hungarian empire, The Man Without Qualities, calling it “one of the two or three novels that I love most.”
At the same time, he was overwhelmed by its size (one English translation runs over 1,700 pages):
But don’t ask me to admire its gigantic unfinished expanse! Imagine a castle so huge that the eye cannot take it all in at a glance. Imagine a string quartet that lasts nine hours. There are anthropological limits—human proportions—that should not be breached, such as the limits of memory. When you have finished reading, you should still be able to remember the beginning…
Take the time to tell your story. If you think the crucial conversation that highlights everything your characters have been going through needs to be forty pages, then forty pages it is.
But keep an eye on the overall work. Don’t make your readers slog through so much to get to the end that they forget the beginning.