回复:pjiang & 各位大侠: 请教绿卡持有者在美180 天的问题

1. is safe, because it will be hard for USCIS to accuse you that you have abandoned US residence if you live in US most of the year.
2. you can do that may be a couple of times, but if you continue, sooner or later, CBP will warn you or even take away your GC (you may be able to get it back before an immigration judge)

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