The doc recommends not to take for more than 2 weeks
consecutively.
Actually 1-3days enough, i really don't see the need to take for
weeks or months. Yes, doc recommend not more than 2 weeks, because
usually when doc prescribe, its higher dose then what's available
over the counter, in low dose, over the counter version, its still
ok for up to 3 months.
But different people different.
Melatonin used to treat secondary sleep disorder, ie jet lag,
shift work. But if really need weeks to adjust that's more likely
that u have primary sleep disorder.