Some online research says that once you see the skin cracking on a few of the fruit, they are probably all ready to harvest. These seemed to show the classic signs, so down they came. I have been munching the seeds each time I pass them on the counter top.
Our tree is still quite young, but it gave us 3 nice fruit (those that survived the squirrels) 
Gave it a quick shape and prune today so it is ready for Spring.
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