Oh, I've been hitting the neti hard for years now. I even moved up from the neti to an electric 'water pik' sinus irrigation system. It helped a bit, but no cure.
The problem with me is that when my immune system crashed due to metal poisoning and candida, some fungus got a foothold in my sinuses that I haven't been able to break since. Even though my immunity has gone way up. Apparently fungus can actually sprout roots into your cells, which makes it impossible to 'sweep away'. That's why sinus surgery never works permanently.