I think that the Wayback machine supports either an HTTP status code or meta tag that causes it to not serve previously-cached contents.

Therefore I try to save webpages that I care about, but it's getting harder and harder. Not to mention the space it takes - is it really worth the hundreds of GiB of personal archives when I'll likely want - not need - maybe a few KiBs of it decades down the line. And even then, will I be able to find it?

Sometimes I think about just archiving a screenshot and the text of websites, instead of markup and related files.