I know this used to happen and Rob disabled it a few years ago; but would it be possible to implement automatic thread locking again? If thread hasn't been posted in, say, at least sixty days, the thread gets locked. If the OP wants the thread re-opened then they can ask the appropriate forum moderator to do so.

As you correctly referenced, this setting was changed intentionally to allow discussions to continue for longer. I have re-activated this feature and set the time period to 365 days. If there is an interest from members to continue a discussion we don't generally have a reason to stop it just for the sake of it, it may be that the thread is still helpful to new members, something has progressed in the topic, it's generated new questions, etc.