Comment by kjellsbells

Even if you are content at your job, there are risks in staying for very long periods of time.

If you've ever joined an org where key people have been there for decades then you'll know of the immense amount of interior knowledge that these folks have. At best, they become instituional memories of the org, at worst, a cabal. The worst case is obvious: you can't get anything done barring their approval, and as a newbie you aren't in the club. But the best case is more insidious: because of the long timers, no one has documented processes, recorded the special tricks needed for the job, or done a simulation of what would happen if one of these key people were to evaporate. (And it does happen, because after 20+ years on the job, they are at the age where sudden death strikes happen, eg heart attacks.)

If you become one of these people, great, but you may find that you have expert knowledge in a very small domain, which is difficult if you get laid off. Which brings me on to my next point.

If you stay at a place for a long time, you are going to build a network of work friends, who, naturally, also stayed at the same place for your tenure. This is great, but also dangerous, because the network of people who can help you find a new job are not dispersed and at the same risk of layoffs as you.

If you work in the widget industry, and you and all your buddies work for WidgetCorp, what happens when WidgetCorp lays you off? Who do you call to start finding work in widgets? You need a diaspora of people in your industry who you knew from WidgetCo but who moved on to WidgetInc or whatever, and likewise, you yourself can be that person by moving on from your company after a few years.