I think I'll also do that with links in every blog post that is more than, say, 5 years old. Opinions differ widely on what the half-life of a link is, but it is Not Long because Everything is Terrible.
It would be nice if there was an easy way to detect whether a site is still really there, and only replace it with an archive link if not, but that's basically impossible to automate since so many sites turn into domain-parking spam pages.
By the way, there are many ways to tell the Archive to save a page immediately. The easiest way to script that is to just load
The Archive is a critical piece of infrastructure of both the Internet, and increasingly, our society. Give them money.