What should we do with threads that were started by users who don't ever come on anymore? For example, I noticed that Evening put one of Liagiba's threads on her list of threads to be locked, and Liagiba has not been on in a very long time. Should we go ahead and lock those threads if we don't hear from the user within a certain amount of time?

Yes. Give the user a week or two to reply to your PM announcing the closing of her thread. If she does not respond to you within that amount of time, edit your PM to say that you have closed the thread and you can leave the PM sit there for whenever, if ever, she comes on just so she knows. Sound good?

Okay, thanks!

Right, if they come back and want it back, we can always un-archive it.

They wouldn't have been there to read any replies anyways.