Cut it early, It may not be ready.
Cut it late, you may not have enough time for it to grow to make another cut.
So 7-14 days sooner or later is that much difference?
BTW, I understand a farmer that has crops in must harvest, BUT I'm mainly talking about the small-time cattle farmers that have 20-50 acres of hay and a few dozen head of cattle.
What about the flush bar?