I prefer keeping everything in one file as well, since even the act of creating a new file is sometimes enough of a hassle for me to skip jotting something important down.

Question for fellow one-file'ers: what do you on mobile? My problem in the past was that all plain text editor apps on iOS open files at the top, which meant scrolling all the way down every time I opened my notes file.

These days I use NotePlan, but I don't really use enough of its features to justify continuing my subscription (the dev is really great though).