You have to compare this with the global savings made by using Flex/De-rate on a daily basis.
Ok then, let's compare. What, exactly, is the saving by using reduced thrust? Your F1 analogy is invalid, because the F1 engine performs at max for it's entire life. Max thrust used for take off would be in a burst of about 1 minute for an entire flight (of potentially 13 hours or so, as in the EK407 case).
Can you see what I am getting at? I'd just like someone to come out and declare that the risk numbers have been done, and that crews are aware of exactly what risk they are accepting. I'd expect that as airlines are big businesses with large sums of money at stake, someone, somewhere has done this.