My dad had a slow progression about 20+ yrs , things are a bit trickier, but still good days and smiles happen..

If at any time you notice possible side effects appearing or getting worse - call his PD doc and let them know.
My dad's doc is always good about adjusting or stopping a med if adverse effects happen..

Sometimes a med will even be fine for weeks, months or longer and then it will start to cause troubles..
It can be a bit of a try & test to see what works best case by case..