I think that the comfort zone is an obstacle to our self-improvement. However as we age, perhaps, we are not willing to change the comfort zone we have built for long time. For instance, I want to change department in my company, but I am not sure whether another department would be suitable for be. I alraedy have a comfort zone now. My inner voice says no need adventure.
I think our comforts change as we age and we become less risk-seeking. It could be that experience has warned us away, or the risks we thought we took well, we actually didn't do a very good job of it.