I am not new on Minoxidil but how long do I have to use this is? Is it possible to use more than 20 years? MOR F 5%

Yes, you would need to continue using Minoxidil to keep your results. This needs an in-person evaluation. I suggest seeing a hair loss expert to evaluate your current treatment plan, results and best options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

Yes, ıf you have a benefit from minoxidil , you have to use it for life long or as much as long time. If you stop to use minox after a long time usage, you may experience a fast thinning, even loss of hair because of ending action of active ingredient. That phenomena leads people to a misconception that minoxidil causes hair loss after  stopping to use it. 

There are a number of myths and misconceptions when it comes to hair loss. If one stops minoxidil they will lose the hair they gained and quickly catch up to what their hair would have looked like had they chosen not to use any treatment. But this is not specific to minoxidil- any treatment that helps androgenetic hair loss will lead to hair loss once again if that treatment is stopped.All treatments for genetic hair loss are lifelong.