Where do you keep them, and do you wish they were better organized, or do you get something out of the chaos?
I pay for Obsidian sync having found it a lot more straight forward to keep things synced between 3 computers and a smartphone than the git sync client (occasionally would get git sync errors)
I've had them in Notational Velocity, first as .txt files, then in the program's DB, since 2006, stored as .txt files in a "Notes" folder before that, and as a pile of "stickies" before that (not sure about the exact name but my default color was always light grey).
I don't synchronize them between machines because I only use one. I don't have them under version control because version control is not backup. I don't have them on a USB drive because they are not relevant when I don't use my computer. I don't use a hierarchy because it doesn't work well with informal notes. I only use tagging very lightly because the effort is not as rewarding as those old Lifehackers posts made you believe. And I back them up like the rest, though not as seriously as I should.
NV's search and general UX are awesome so whatever information I want to get out of those decades of notes is always a few keystrokes away.
(FWIW, the latest release of Notational Velocity was 13 years ago and still works like a charm after 11 major OS releases.)
Jesus, that's impressive.
For more secure information that I want to be more portable I use tiddlywiki on a USB stick.
So now I use: https://github.com/nuttyartist/notes
I'm working to get the git-auto-commit program I wrote a couple years ago working again, to version control the history. There's now a git auto-commit built-in too, which I only noticed! Hopefully works well enough or is improvable enough for me!!