When did you know it was time to move on to another unit?

I was all set to transfer out of my unit after 4 years, but I then decided to stay. There were personal and professional considerations, however the main reason was the new TAG has been set on bringing changes after the old one was in command for nearly 20 years. And for the betterment of the organization I felt I had more to contribute. But when I got a new job as an Army contractor I started to see all of the other very intriguing opportunities in my AOC, I started thinking about other opportunities for advancement. My goal has been to establish a good solid program to fit the needs of my state and I have done that. Now I have been feeling like I should be planning my next step in my career. When did you know it was time to move on to another unit? I think this is more of a small state Guard issue but I am curious of peoples thoughts on the topic.