I gave up on considering the web to be a "web" of hyperlinks. These days the www just feels like a collection of siloed (namespaced) applications. I expect a link to be valid at least long enough to use in an email (i.e. days/weeks), but I wouldn't use a link in say a blog post without also copying the relevant information out of the page. The url is then just a source reference identifier, not a hyperlink that is expected to go anywhere.