Anecdotally, I am taking it for years and haven't noticed any reduced effectiveness. Effectiveness increased when I reduced the dose to 0.3 mg. and started taki

Anecdotally, I am taking it for years and haven't noticed any reduced effectiveness. Effectiveness increased when I reduced the dose to 0.3 mg. and started taking it several hours before sleep. https://slatestarcodex.com/2018/07/10/melatonin-much-more-than-you-wanted-to-know/ https://slatestarcodex.com/2018/07/10/melatonin-much-more-th... is pretty much a required reading on melatonin, as well as https://www.gwern.net/Melatonin https://www.gwern.net/Melatonin. Neither discuss tolerance at length unfortunately.