One of the main defferences between a 2,000 hour pilot and a 20,000 hour pilot is that the high-timer has made at least 10 times as many mistakes. Regardless of age, it is all about one's experiences and how well they accept the advice and relate to other pilot's experiences to be constantly enhacing their own. Some pilots will catch on to things quicker than others, but I feel that we all learn through experience, and how better to learn than from the mistakes and guidance of others?
I've never flown 121, but I've had a few Eagle Jet Int'l timebuilders ride along with me while flying skydivers and it usually takes a few flights to prove myself, as a younger pilot, but once the older guys figure out that I have decent flying skills and judgement they tend to respect my position as PIC more as they fly the plane to log time.
The same thing would go for instructing older students. I could tell that they were a bit skeptical at first due to my age but once they could tell that I knew what I was doing, it was business as usual.
-PJ