This for me is the selling point of the Flex FP. If the route has a few flights a day and I'm a little flexible, I can get a pseudo-Latitude for basically Tango price simply by not booking until I know my plans won't change. On my route, other than big holiday dates, there is usually M available on at least one flight a day and the biggest deal for me is selecting the flight that will upgrade on booking rather than waitlist me.