The U.S. Food and Drug Administration does not strictly regulate herbs and supplements.
A problem with judging the quality of these products is that they are mostly reported by the company promoting the product. The "studies" these products often refer to are funded and run by the company itself and may be biased and lack control groups and randomization.
In my opinion avoid long-term excessive intake because it may result in side effects.
So if your boyfriend is taking this supplement i would suggest to take it for a shorter duration.
Usually they don't cause any sort of addiction.
I hope this helps
Short term course include 30-45 days.
Long term means 3 months or more.