It is NOT useless Gromit. It works for both me and my daughter but not for my son. Taken occasionally by both of us.
Our body naturally makes Melatonin but this ability diminishes as we get older. I have a bottle of low 2mg capsules on my bedside table and I will take one when I feel it necessary. If I'm still awake at 3am then I will consider taking one but never more than 3 days in a row. One reason for that is because they give me nightmares if taken any longer without a break.
I do go months without taking any at all, one bottle will last me 2 years. Taken in moderation after checking they don't clash with any of your other medication you should be fine IMO. I've been taking it for at least 13 years.