I've been where you're wondering about, but had to be practical as to the timing because of my fed retirement credits still needed. I finished my 2 years needed to retire from Congress at the earliest official timing allowed, then made the jump to the television news industry at 54 years old (my strategic plan to lead to my ultimate goal). BUT - to your question, here's my reply:
You may be hearing inside the call for change when...
You have reached the pinnacle where you are, with no more growth, no opportunity to leverage, no learning of new expertise, and you are just 'marking time'; and if transition keeps calling to you inside and there is something different you really want to pursue (you can SEE it), it just may be that you are ready to go to the next level/next horizon in your Life Journey. Take careful inventory (of what's leading you). Don't confuse restlessness with a need for change. Bottom Line is this: If you thrive on challenges and have a thirst for expanding your base but it's not available where you are, then you are a candidate for change. All of Life is Change, and that's where you find your personal and professional growth. All else is stagnation.