This may not be the popular advice, but hear me out.
A friend of mine was joining the corps with me (buddy program). Our recruiter told him the best advice of his life. Push it. Run and run and run. Work out. Push your body to get used to it, and push through the pain. Granted, it's EXTREMELY advised to still have some form of inhaler / support / etc.
My friend and I went through 3 tours together and he didn't have one outbreak that I know of. The only people that know are our recruiter, me and him.
Long term fix, takes a decent amount of time.
Since you haven't had a problem in an eternity, I don't picture this being hugely difficult for you to achieve.