Frequency for PRP hair loss treatments? Does it make much of a difference if you go 4-8 weeks between treatments?

Frequency of treatment depends on the amount, type, and method of use of PRP.  This is variable in various practices.  Typically approximately 13ml of PRP is needed for each half of scalp.  The type and kit of PRP used is also very critical.  Generally treatments can be every 9-12 months with an optional booster 3 months after the initial therapy has been shown to be helpful. 

Hello Larry832,
Hair regeneration is relatively new. Therefore, you will hear many methods. Hair reduction has been around much longer. Simply follow the same cycle to grow hair as used to kill it.  
The number and frequency of treatments is important. Hair grows in cycles. It is either dormant, active or going into or out of activity every 6 weeks or so on average. When dormant, we can't even kill it with a laser. Therefore, we can't make it grow or stop them from going dormant.
Therefore, I recommend 4 to 6 treatment sessions spread 5 to 7 weeks apart. This should affect all follicles that have a chance at regeneration. Yes, this is a tad aggressive. However, it provides for optimal results.

If you don't see much of a reaction 5 - 6 weeks after the 2nd treatment, you might consider saving some money. Certainly, if 6 weeks after the third treatment you don't see a benefit, I would discontinue and save money. Keep in mind fine hairs is a good thing, they can turn into regular hair when properly nurtured.
Consider adding Propecia and Minoxidil to your regimen. The side effects are applicable only to a very small portion of the population. I encourage you to try them. However, not together at first. Try one first and see. If no problem, then add the second. Start with Minoxidil.

Most importantly, investigate what your hormones are doing. For example, if your DHT is too high, it will work against and possibly inhibit your hair regeneration and longevity of the treatment. 

I very much encourage you to locate and visit a good Integrative or Functional Medicine physician. They are trained to get your hormones and metabolic system optimized. There are a number of methods they can employ to push down inhibiting hormones such as DHT while pushing up beneficial hormones. 

As a side benefit to your quest for great hair, these type of physicians will have you feeling much better as well. 

Consider adding a extracellular matrix (ECM). ECM's will supercharge your results. 
Photo/Light therapy; you can either locate a physician with a light therapy device or purchase a good light cap and use it a few times per week. Don't go with the cheap ones.

Maintenance; The life of these procedures is generally unique to the patient. They generally last between 12 to 18 months if not using photo therapy and hormone management. I don't like to wait this long because it means were starting at or near zero again. Be proactive.
Therefore, consider having a maintenance treatment every 5 to 9 months as appropriate for your condition. Above all, don't wait until you see the restart of hair caliber thinning or loss. Should you do so, you may need to start a whole new cycle of treatments. Don't forget to keep your hormones in check. Doing so will prolong the life of the procedure and is cheaper than the procedure. 

Make sure the practice is using high density PRP. Generally the yield from a 50mL blood draw is about 7mL of PRP, equaling a 6 to 7 x of base. 
I wish you all the best in your quest for regaining your hair.

Warmly,

Arbella Saris, MD