I have been saving seeds for a few years now. Mainly because I can never seem to get fresh seed here locally that I want for late summer and fall sowing. It seems I am in an extreme minority here in that I actually keep my garden growing year round despite the cold winter and snow, using low tunnels and fleece as needed.
There are many over winter crops that do well here, and one is fall onions. These will over winter and be ready to harvest early in late winter and early spring next year. I also find, for me at least, that starting onions from fresh seeds leads to larger summer onions over onion starter sets.
Mid summer is about when the onion pods begin to release their seeds and time for me to harvest them before they drop to the ground.