Seed production under long hours

I'm helping to produce a large fem seed crop in a greenhouse using a light dep tarp to create a 12/12 cycle. The plants are at peek flower (maximum pistil formation and pollen applied). Natural light right now is about 15 hrs. What will happen if we stop pulling the curtain? Will the seed mature normally?

had a veg plant that was pollinated early on. i had a similar question. i have been told that seeds can mature in vegetation stage an do not need to be in flower.