Auto-Lock thread (archive) after X months of no activity? (Dead thread bucket)

Basically, it's an "administrator" request, or feature request. Once a thread reaches an age (say 6 months or a year) with no new additions, it "locks" so we can't "necro" it, or respond to it.

We'd still be able to search it, or link to it, just not "raise the dead."

Your thoughts?