I heard, but never found any writing anywhere, that a green card holder needs to be physically inside US more than half a year for every year, otherwise he may lose his status. But I have been outside US once(to Canada) since I got my green card stamp(I551?), I am wondering how could INS know how long I stay outside US? Because for my above mentioned trip to Canada, INS did not mark anything for my departure, they only stamped my passport for entry. So how INS know how long I have been outside.
Is there anywhere, like in Immigration and Nationality Act, enforce that a green card holder should stay inside US half of the time each year in oder to keep his green card status?
Immihelp, could you please spend some time here and give your insight?