Six weeks later, the mint seemed about as extracted as it was going to get and I now have nearly a liter of decidedly green mint extract:
Correspondingly, the leaves turned from bright green to dull brown:
The smaller and darker pile in the rightmost bowl came from the smaller jar (on the left) with a higher alcohol-to-leaf ratio:
Perhaps packing the jars before pouring in the alcohol doesn’t extract as efficiently. Or maybe, as in so many things, it doesn’t really matter.
A liter of mint extract may not be a lifetime supply, but it’ll suffice for quite a while!