回複：請教皮匠，拿到綠卡後每年入境美國一次的問題

For GC holders entering US, if out of US for 6 months, do expect to provide a reason why you need to stay abroad so long. If out of US for 1 year without RP, CBP should take away your GC and you will get it back (or lose it) in front of a immigration judge.