I have to admit, I like long files. Arc's compiler is all in one file (https://github.com/arclanguage/anarki/blob/master/ac.scm) and it was a big influence on me. It was just so great to be able to have it open on one side while I wrote programs in Arc.

You're right that there are points beyond which a single file becomes too unwieldy, but with a good editor that limit is quite high for me. Maybe 10k LoC. Directories can grow even larger before they start having problems.