> I am always shocked when I learn the some code I wrote as throwaway-tp-be-done-right-later 10 years ago is still in use.

That's because your "quick throwaway" code solves a real problem. It is useful, it works, it is very likely easy to understand.

In short: It's good code.

(It might not be "elegant" or "clever" or even "neat". Those things are overrated.)