My dad had it for 17 years, which is ridiculously long for the type he had (late onset). It seems (in my unprofessional opinion) that (even though they are both called "Parkinson's") early onset, like what Michael J Fox has, takes a lot longer. In my dad's case, I think staying active for as long as possible made a huge difference in moving and living longer.
I know coconut oil has been shown to enhance brain health, and that's a legitimate concern with Parkinson's, so that might be an area worth researching.
Wish I could be more help.