The only thing we all have in common is that no one does the same thing for 40 years anymore. There is a 100% chance that what we do at the end of our careers is not what we began with in the first place. Was your current job a deliberate choice to stimulate your own progress and if the answer is yes: when do you think will you have learned enough and it is time to find a new challenge? Timing is of the essence in all the choices that we make. How is your timing?