八老師您好！首先謝謝您為大家答疑解惑。我們一家17年取得綠卡，我先來美工作，然後先生兒子去年八月份從多倫多來（兒子高中畢業後）。我兒子一直很想念多倫多的同學朋友，這期間節假日數次往返於美加。現在他打算轉學回多倫多大學，我們多次勸他都無效，這個年齡的孩子很讓人無奈。請問八老師，如果每年寒暑假他都回美國，是否能夠保住綠卡？每年在美國居住多久才可以保證綠卡在有效期內呢？多謝八老師！祝您週末愉快！
-He can file I-131 to apply for reentry permit (RP) which allows him to stay outside US for more than one year but less than two years. He can come back to US to renew the RP before it expires. Read the I-131 Instructions for RP application. He can leave US after conducting the fingerprinting if the time is urgent. Of course, he also can visit you anytime during his study in Canada using RP.
