What I can tell you comes from my Mom having PD for 20 years. Each Parkinsonin is different and there is NO definite time frame for this disease. There are 5 stages that can be identified, but no way of knowing the length to each stage. So please don't be afraid of what you read here, Mom is 82 yrs old, 20 yrs of PD, legally blind and can be difficult, but there are still times when we have golden moments.
Knowledge and understanding of the patient and the disease is the best way to handle what lies ahead. Respect those days when your mom will need to rest, be active on the good days. Be her advocate when it comes to the health care. Just be there for her, such a simple concept, but difficult to fulfil all the time.
Good thoughts to you and your Mom...