I tried to wax my head using some lady leg wax last year. I did it at the end of September with a lot of pain and little result so I tried to let it grow longer like the instructions said. I waited a couple weeks and tried it again and a few hundred hairs came out but it wasn't noticeable. About 4-5 days after doing it for the second time I was washing my scalp which was very sore and looked sunburt I used a scrubber on my head with axe exfoliating body wash and hair was just falling out like crazy. I quickly earned the name 'patches' at work because I had tons of smooth patches that were random sizes/shapes. That was in the middle of October, the hair didnt start to grow back in the patches til early March.
If you get it waxed successfully it would last a couple few months atleast.