Thanks for the reply - so I would summarize by saying you are mostly using f.lux as a cue to adjust how alerting the display is right before bed, and not to "shift" your circadian timing.
We think probably 20-50% of the population needs some "phase shift" adjustment (meaning you would want f.lux doing something more aggressive to the light you see), and some of those people need this only at certain times of the year. Some people are just close enough to 24 hours that the only thing we can do is exactly what you describe: tell them it's bedtime and get them off the internet. :)
For the others, the big trends are that younger people (in their 20s) often have very "long" internal clocks and require a bigger push to earlier timing, and some people later in life have a "short" clock that makes them wake up too early. Also with age, we know that the sleep drive can be somewhat lower, so people have more interrupted sleep.
And yes, the body's clock is now thought to be just slightly longer than 24h for most people (about 24.2) - the 25 hour number was for people in constant light, which is not what most people do.
But we think (basically for anyone) maintaining the "right" light-dark cycle (more light during the day and less at night) will improve your ability to fall asleep and your ability to sleep through the night, but we have a ways to go to show that this helps every kind of person and not just some.
