It's not easy to get permanent staff nowadays. All employers would hope that their employees would stay and work till they retire. But in reality, this won't happen. Most employees will only work for a certain period of time before they change their working place.
As for me, I had worked in different places before. All because of better future ahead. So I believe it's good to change job after a while as it might get monotonous if we stay longer. We wouldn't want to burnt out..