I discuss melatonin's effects on sleep & its safety; I segue into the general benefits of sleep and the severely disrupted sleep of the modern Western world, the cost of melatonin use and the benefit (eg. enforcing regular bedtimes), followed by a basic cost-benefit analysis of melatonin concluding that the net profit is large enough to be worth giving it a try barring unusual conditions or very pessimistic safety estimates.
Full essay: http://www.gwern.net/Melatonin
Which studies do you find particularly convincing? Cochrane has only meta-analysis of short-term melatonin use for jet lag, which I don't doubt.
Which studies show that melatonin allows long term reduction in need for sleep, and that this sleep reduction has no negative consequences?
Saying you need "less time for sleep" only applies to people who have difficulties falling asleep, and needs some evidence anyway.