This seems like a very clever way to use points, no?

For example, we want a BOS>DCA ticket in the evening, that is running $350 or 29,900 points per passenger.

We can however redeem 11,500 points for a Blue/Flex ticket that morning (or 7,400 for a regular blue ticket, but then we'd have to pay $75).

We then stay up until 12:01 a.m. on our departure day, call jet blue, and as long as there are open seats on any of the afternoon/evening flights going to DCA or IAD, we can move to those for free?

Obviously we have to be prepared to take the 6 a.m. departure if there is a total sell-out (cancel ticket for a full refund since it's a flex ticket).