Those are all things you generally do at home and therefore would look up with a computer. On my computer I’ve been hoarding textbooks, datasheets and manuals for quite some time. I’ve been hoarding scientific databases like protein db too but it’s a pain. Everything on the internet is ephemeral. If you value this information you shouldn’t rely on someone else to host it for you.

optimal choices for product buying at a moment’s notice with an encyclopedia

If I’m out and about then I don’t need to find the “optimal product”. Either it’s a big purchase I already researched or it’s a small purchase where the primary consideration is quantity of product divided by cost.

In fact when datahoarding I find that reference books published before the internet are generally more convenient because it’s all self contained and meant to be navigated without search. For example a book with tables of stress-strain curves is more convenient to store because it’s just a pdf you can easily search through manually, versus a modern database you probably have to scrape off some website, usually in some annoying format you need specialized software to deal with and have to spend an afternoon installing packages and writing scripts just to look at it. And when an update breaks the delicate python environment you need to run some janky library for this specific format which could’ve just been a CSV you’re fucked.