A reasonable career trajectory is something like doubling the time at each place until you hit the 8-10 year mark, modulo uncontrollable events, like a place sh

A reasonable career trajectory is something like doubling the time at each place until you hit the 8-10 year mark, modulo uncontrollable events, like a place shutting down. When you have someone who's been repeatedly changing employers every 12-18 months for a while with no mitigating factors, you begin to wonder about ability to commit. It may matter less if your are in a field where things are done in sprints, the person is likely to be instantly productive, and there isn't a lot of complexity to absorb. There are people who have the temperament to be short to mid-term contractors, and who don't like to be and wouldn't be good long-term hires.