Your career, product, and company might follow the shape of an S-curve. There's an initial dip, growth, and then decline.

Charles Handy wrote that you should start a new curve (aka new direction, focus, job) before the first curve reaches its peak and subsequent decline.

But everything is going well at this point. Why would you change direction? It's easier to see the need for change when in decline, but you may not have the resources or time to implement change.

There's no science to figuring out when to start the second curve. You need to start preparing when you have resources and follow your gut.