There are over 10k of such files I've saved in this manner. With practice it becomes second nature to categorize and tag them just using the filename, which makes them findable within seconds.
These have become like my own private search engine, without the issue of not being able to find answers to queries you know exist (which increasingly has become an issue with online search engines).
In Chromium the saving to MHTML feature is enabled by launching the browser with the CLI argument `--save-page-as-mhtml` (Vivaldi browser enables this by default without any arguments needed). Firefox used to support it via excellent addons up until their Quantum update but they haven't supported it since and is a dealbreaker to my daily use of it.