It seems policy here to explicitly close threads when OP thinks enough information has been posted. Currently it takes time from both OP and admins to actually close the thread if OP considers it closed.
To close a thread, OP has to take significant action: decide who to send a message to, come up with a text, type it down and hit the send button. It's a lot of work, while the contents are always basically the same. If OP is the only one who can decide about this (outside of mods and admins), then it would make sense to create a link or button that allows you to request the thread to be closed. Relevant people can then take action, close the thread and be done with it. Or, if admins/mods will always close a thread upon request, why not just allow OP to close the thread directly?
If closing threads is the way to go, to me it would make sense to close a thread automatically after say 30 days of no activity, if that is not already done.