This rule does intrigue me as well. Part of me says it's useless, the other part of me says it should stay although it can't put its finger on "why."
Thinking about it... In the end, I do kind of understand why we have it in place. I can't speak for the staff who've made the rule for whatever the reason they did, as this is my own interpretation... But I see it like this... Imagine some of the current Debate threads we have now. Some of them are a 100+ posts long, and excede 15-20 pages. So, it dies, people have moved on from the discussion. Imagine some - usually new - person that comes along and re-opens the discussion. It'll be like hell. First, you'd have a 25 page thread that's been discussed. Secondly, most of the people originally posting on it have moved on from the thread, leaving it seemingly empty of discussion despite being put back on top of the thread list. Thirdly, the people who have never seen the thread before, will probably skip reading anything, and go straight into posting. Whatever they post will most likely be the same crap that's been said 3 and 4 times in the original 25 pages. It'll go on nonstop. Every 3 weeks some guy will come in, look at older threads and bump them.
So, from that perspective, my own, I can see why we have the rule in place. And, as I was posting, I convinced 100% of me to keep it. Thus, I vote "No" to abolishment.