How long can I stay out of the country if I have a green card?

Remaining outside the United States for a year or more triggers a presumption of abandonment. However, lesser stays outside the United States can be problematic. You are expected to reside in the United States when you are a lawful permanent resident. This does not mean you cannot travel but you are expected to spend more time in the United States than out. You should plan to face secondary inspection upon your return. You should be prepared to both document and speak about your travels including why you have spect so much time outside the United States.