According to some, Melatonin should not be used long term, because it weakens your body's ability to produce it on its own. Might be good to pulse it.

BTW, heard somewhere that cannabis increases melatonin, but don't quote me on that. I used high CBD cannabis at bedtime often.

Magnesium is best at night. Also some forms are supposed to be better absorbed than others. I take Glycinate.