I haven't needed to harvest bin 3 until now but it worked out fine because I was able to confirm a hypothesis of mine. I had put too many leaves in to make sure there would be no odors, and that just made everything decompose slower. So, letting it sit longer, I assumed would produce dark, rich humus unlike what we got from previous harvests. We let the first bin sit for 19 weeks, and the second for 20 weeks, while this one had been sitting for 35 weeks since it was filled. It worked! We got loads of perfect humus.
Also, as you will see in the pictures below, we sifted the compost finer this time, which gave us better final results too.
So, the lesson is put fewer leaves in the mix and you won't have to let the compost sit so long. If you put too many leaves in, then let it sit longer. Simple.
Here are some pictures from today's harvest.