I think they'll gladly keep the holders of these visas as long as they're desperate. It's not about length of time, it's about keeping them tied to a single employer, working like a rented mule, afraid to speak up. These visas make people good, docile employees because if they aren't they get removed from the country. It's kind of wild that they are so casually accepted.

Exactly. It’s designed to allow you to work for a time and then return. They’re nice enough to allow a spouse to accompany, but not to work or remain.