For permanent employees, the more total experience there is, the more a job hopping trend becomes visible, and even ~3 years looks too short. E.g. Looking for a new job after 2 in four years doen't look as bad as someone looking for a 4th job in 9 years. Apart from the onboarding and offboarding costs, which the company has to foot, having many samples says a lot about the employee. It says that they either weren't valued enough by the company to justify market related increases, and/or that they were likely incompetent and/or the employee gets bored easily and/or chases incremental increases due to a constant expectation of not being valued. Sure, companies are often to blame, but with enough total time, the only invariant becomes the employee.