Thanks for the answers folks.

I used to fly an E90 with a 76 yo who was every bit as sharp as any pilot I've flown with. Insurance dictated he have a co-pilot in case any medical emergency occurred ---which I was very fortunate to fly with him. He was a very accomplished pilot who had the best stick and rudder skills around. I had mimimal multi time when I met him and he was an amazing pilot who was an excellent instructor and mentor. We operated under part 91 based in the midwest and flew west to the Rockies and all over the East and Gulf Coast. He has taught me more about King Airs than any school I have attended. I believe us younger pilots should use the older pilots as a resource to tap into and learn from as long as they are mentally and physically able to perform the duties of piloting and pass the medical exam. I still use my "mentor" today as a wonderful source of knowledge of King Air operations.