I don't feel any physiological dependence, as I go on and off it with no consequences that I can detect (other than becoming more prone to slip off my sleep schedule). Generally I only take melatonin daily when I'm adjusting to a new timezone/schedule or have lapsed by purposely staying up. Otherwise I use it maybe twice a week, and have gone months without any.
When I don't take it my sleeping time seems to be a function of sleep hygiene.. Your melatonin production cycles are probably most strongly controlled by zeitgeber factors, like the mentioned blue light wavelengths. My insomnia used to be as bad as yours and now it's fairly normal for me to fall asleep at 1am, even using the computer. Once you get in a pattern, it has some persistence to it.
When I don't take it my sleeping time seems to be a function of sleep hygiene.. Your melatonin production cycles are probably most strongly controlled by zeitgeber factors, like the mentioned blue light wavelengths. My insomnia used to be as bad as yours and now it's fairly normal for me to fall asleep at 1am, even using the computer. Once you get in a pattern, it has some persistence to it.