Consider this, as coaches we bring forth years and years of our own personal experience and a belief system based on the information and situations that we have been presented through out our career. As a coach/mentor, we must not look at this dynamic as defining our credibility but revealing our limitations to what we know (or really, what we don't know).
I learn new things every day. If I am not consistently challenging myself to find new content or a better way to do things, I'm cheating those that have entrusted me with their careers. Coaching is about adapting to the individuals and information at a present moment and the information we have changes, daily.
As a coach, it is our responsibility to continuously seek out ways to make ourselves better but in that same instance, surround ourselves with people and resources that make ourselves better. Why? Because no one, not one person, is a complete coach. We need the ability to collaborate and challenge our ideas, that's how growth happens.