I have read that PRP Acell only last 3 to 6 months and I have also read that it can last 3 to 6 years. So which is the correct?

As I know Acell is not FDA approved for hair loss and hair restoration patients in the USA. However the use of autologous PRP treatment for hair loss involve too many variables such as: centrifuge, platelets activation, platelet %recovery, treatment periods etc. There are few studies that show some results as hair loss therapy. I usually recommend PRP treatments every 2 months for 6 months then maintenance every 6 months. Minoxidil (women) and Finasteride /Minoxidil in men are great combination treatment + PRP for hair loss. Obviously there is still a role for additional hair transplant surgery  in many cases. 

Nobody knows that answer. My patients will tell you that increased shedding starts up again at some intervals after getting PRP indicating that effects are fading. Minoxidil is twice daily. Hormone blockers are once daily. Laser is three times weekly. Is it likely that PRP is potentially be 4000-5000 times more potent than these therapies when we can't even figure out yet how well it works? I'll leave that to continued and open discussion - and of course further good studies.