Age might make a difference as well as the severity of the disease. My husband was 80 when diagnosed and stopped driving about 2 years later. He had shown signs though for several years that we assumed were just age related. It wasn't until he was falling regularly that he agreed to see a neurologist. Someone who is diagnosed younger may go 10+ years without significant progression so would be able to continue driving much longer.

Two years

I was diagnosed in 2019. I gave up driving in 2022 for other reasons when we moved to Texas. My brother was diagnosed in 2016 and is still driving. I think it will be different for each person and their symptoms.

I'm 90 years old and still driving my Tesla. It drives itself on the highway, but I don't trust it of back roads. My 78 year old wife (who also has Parkinson's) had to give up driving, because her reaction time was poor.

I was diagnosed about eight years ago. I'm 73 and still driving my SUV. I still own multiple motorcycles, but stopped riding them when I was diagnosed with Parkinson's. I was starting to have balance issue's and didn't want drop one of my bike's. I rode about 25,000 miles a year for about a have a century. I miss it, but just can't take the risk anymore.