Dead Threads

^ I usually tag the thread if it's a year or older because a lot of the posts people reply to are from users who may not even be around anymore. Other times, I'll tag/merge threads if it's something that's been mulled over time and again (i.e. Ayumi's eyes, her 'rivalries', etc.). Also, older topics often bump recent topics, causing people to repost a thread because they don't bother reading two pages of thread titles, so I also tag the year for that reason.

As others said, use your judgement and try not to rehash old arguments. But for album stuff, that's fine (although I find many people have changed their opinions over time).