Your babies have a ways to go. I wait until the cone petals "open", lupulin is visible near the strig, and the petals have gotten to the "papery" stage. By that time there are some huge cones, and depending on strain they could be closing in on four inches long. Keeps things interesting
You can see in this pic the petals have gotten some space between them and aren't all just laying down tight together.
Once you see this, it won't be too long before they start getting that "papery feel". You can push on from there and wait until a few cones start getting brownish tipped petals, then call it and start harvesting.
The presumption in all of this is that the further out you can push the harvest the higher the lupulin payload, otherwise you could harvest any time you got the urge