The trajectory of a product management role is somewhat predictable. You walk into a chaotic, out of control environment. You bring in phases of order, and after a couple of years, and two or three successful programs things are looking pretty good. The crises are way down, engineering and marketing aren't hissing and spitting at each other, and in general all parts of the organization are working well. All in a days work for product management. But how are you doing?
At this point, things are getting, dare I say it, normal? You have a cohesive roadmap, prioritization is well in hand, and nobody is yelling. Strategy is well defined and all groups are bought in. Sounds like paradise right?
In any other field, this would be when management taps you on the shoulder, and gives you a promotion to the next level. You have proven yourself worthy. But product managers are different. Usually, management knows what you have done, and how things have improved from your first day. They are in no hurry to move you out or up. Perhaps they know how tough it is to get a good product manager. It probably took them two recruiters and 6 to 9 months to find you in the first place, and the last person before you that they promoted from engineering into the role was a disaster. You can hardly blame them for keeping you in the role as long as they can.
If a company was smart, at this point, they would begin the search to replace you, and yank you into their executive career path. But most companies don't do this. Pity, because proven, successful product managers are outstanding executive feedstock. Their loss.
Back to you. You are getting bored with the current gig. The challenge is gone. You can turn on the autopilot, and glide, just turning the product definition crank. Some people can do that and be happy, but most of us get antsy. Perhaps it is because good product managers are a little bit ADD, and addicted to the chaos. Or perhaps we want another challenge.
So, when is it time to consider the next step, and how do you know that you have reached that point? It will be different for each situation, but to me, if by the end of your 3rd year in a job, you haven't been able to bring order, the odds are good that it can't be fixed. Time to move on, no question about it.
But what if things are going well? You have taken more and more products under your wing. You are the de-facto leader of product management. If you are lucky, you are able to expand the group and have a couple of partners in crime who are working with you to keep all the programs in line. In fact, often you are able to both increase the velocity of development (reduce the time to develop a product) and the number of concurrent projects (by staggering them to optimize the use of resources). But you are bored. You might be able to transition to a senior management role, but it is very difficult to accomplish that at the same organization.
Time to leave. Do two or three repetitions of this (at different companies) and you can parlay that into a senior product management or marketing role (director or VP). Or hang out a shingle and go hired gun (consultant).
If you find yourself in a product management role for more than three years, odds are good that you have reached this state. If you are satisfied, by all means stay. You have earned a period of time that is less chaotic. But, if you are like me, you see the role like the robots in Blade Runner. A finite lifetime. When it's time to move on, you will know it, and make the jump.