I also enjoy the resurrection of a thread, and the constant zombie warning messages unnecessary. Why do posters get so upset if the subject matter makes for an interesting read?
I agree. There are some threads that don't age well, although I still think the problem there (as so often) is people who don't bother to RTFT - or even just the OP's posts - and wade in with outdated or now-inappropriate comments; but that's perfectly possible with a thread that was brand new yesterday but has since moved on.
We all talk about mansplaining, but there are lots of people of both sexes who assume the psychic ability to know what everybody else is talking about, without feeling the need to see what they've been talking about - coupled with the assumption that their pearls of wisdom will be original and more apposite to the discussion than anything that could possibly have been already made by people who are in the discussion.
Thus, if people are determined to just to blunder straight in at the end of a discussion, it doesn't really matter how old the thread is, as they're still going to post inappropriate and unhelpful responses. Without a way of forcing people to RTFT/all the OP's messages, this is always going to happen. The topic comes up frequently, but usually only results in angry Don't-RTFTers asserting the vastly superior value of their time and insight over other people's. In particularly sensitive cases, MNHQ do plaster a big obvious warning into the title - such as the recent thread where the OP was concerned about her dying DM and then the inevitable sadly happened.
Some people do definitely want to just make a name for themselves as zombie-hunters, though, and seem to quite like the sound of their own voices. Many of the zombie threads are still funny, interesting or helpful, however old they are. As an outsider on a huge anonymous forum, it doesn't really make a big difference whether a stranger had a big entertaining, spectacular argument with a CF neighbour over parking today or ten years ago. Obviously, nobody will be adding specific new advice to the OP anymore, unless they're a committed Don't-RTFRer. Even if an OP is discussing a baby name and the original recipient of that name has now gone on to make them a grandparent, other people are still having babies and choosing names for them, so it's hardly completely out of date, is it - unless maybe it was a time-travel thread from decades before MN even began and somebody was looking for a cutesy nickname for bc name Adolf.