Your body will naturally produce less melatonin at sleep time. It adjusts back if you stop taking melatonin. This isn't an issue at the doctor recommended 1mg dosage of melatonin, but at 3mg it is and most melatonin pills are 3mg.
As a fake doctor of herbal medicine, my recommendation is to take 1mg of melatonin when you want it, not 3mg. Also, if you take it sublingually (letting it dissolve under your tongue) it takes effect right away.
Interesting. I generally take 3mg, and I think I pretty much need it at this point. I may try and lower my dosage over time. That said, are there any negative effects from relying on melatonin? Sure, maybe I can't sleep well without it, but having access to it isn't much of a problem.