Mods are "overworked" because they have made it their duty to close way too many topics.
While in theory you can make the forum better by closing just the right topics at the right time, they really need to reassess their strategy.
Half their work seems to be, closing duplicate threads. I think this idea should be reassessed. For the amount of work it is, it's questionable whether it really helps the site at all to prevent someone from starting a new thread about something that was discussed previously. It's not much different than the thread being bumped, except it gets reformulated. If the thread has enough content to respond to then IMO it should be left open. No one forces you to read it--unless it's poorly named (which can be corrected and perhaps needs to be stressed more than closing threads).
A lot of interesting discussions seem to be closed because a lot of people made shitty posts in them. That's not the OP's fault. Discourage the shitty people--don't rob TL of the whole discussion. People NEED shit to post in response to. Closing threads fundamentally can undermine this.
Finally, there seems to be an idea that a discussion should be stopped if any mod thinks there is nothing to discuss, or nothing interesting to discuss. This is a horrible idea because almost any thread can be closed if the wrong mod sees it and has this idea about moderation. This results in the amount of mods directly dragging down the site. Mods should let others discuss things if they want to, as long as the site is not threatened or damaged. They should be okay with seeing people having a thread that they personally wouldn't care about--or they shouldn't be mods.