Do you still get replies to month old questions? That's impressive. ^.^ But if people don't preemtively pick MHO it won't get closed. It also only closes by itself, if it is inactive for 24hours, so if people reply, it won't close.
What I don't know, is if updates you make, counts against inactivity.
That's part of the newest update. Questions that have MHO chosen already or have been inactive for 48 hours (no new opinions or replies) will be closed. No more new responses will be taken then. Their logic behind it is for us to focus on open questions and ensuring that all questions get responses. I do understand the frustration, though.