Hah! He said brains.
If you post in an old thread people moan about zombies.
If you dare post a thread about a subject that has been discussed before, people moan and give you a load of links to old threads.
You can’t win. People are just moany gits.
Exactly. It’s downright disconcerting to be writing a reply to someone and then suddenly realize that they’ve been deceased for five years, even if they weren’t a close friend. If they were, well, I could see it ruining a person’s entire day.
All threads over one or two years old should automatically be locked. If anyone does have a good reason to post to one, they can ask a moderator to unlock it.
Even if vBulletin doesn’t have this functionality built in, it should be fairly trivial with a scheduled SQL statement.
Most of the reasons I’m not keen on Ye Olde Threads have already been covered (mainly the not liking reading through four pages of backstory before realising the date is sometime in 2003 and most of the people involved are no longer here).
Personally, I’d like to see threads automatically locked after three months or so of inactivity, and if someone wants to bring the topic up again, they can start a new thread and link to the old one.
But most of the thread necromacers apparently just find the thread on Google and maybe glance at the original question before weighing in. Maybe one in 20 might read right to the bottom and see the footnote.
I have done this too, with the same head-smack. 
Most zombie resurrections I’ve seen consist of the aforementioned “me too” posts that aren’t really relevant to an “annoying neighbors” thread that was posted and likely resolved three years ago.
It’s irritating because if I forget to check the date of the OP (which is often, because until the beginning of this year this wasn’t a problem on the scale that it’s become now – why is that, anyway?), I end up offering advice to someone who doesn’t have any use for it, and hasn’t for for years – and as mentioned, may not even be around to read it anymore. I like the community aspects of this board, but it needs to be current in order for it to be meaningful. Otherwise I’ve just wasted 20+ minutes of my time reading a no-longer-relevant thread.
that shows mental stability. maybe a good thing.
after doing that a couple times i trained myself to check for dates going in to a thread i didn’t recognize. most of the time it works.
i’ve seen a healthy number of threads recently where people supplied good answers between 3 and 11 years later.