איך לשמור על הגרין קארד
Generally you need to prove that you live in the US. Even if you leave the US for more than 6 months if you can show that you filed your taxes and hold a property in the US that will be a decent proof to the officer at the border when you plan to return.
Normally, being out of the US for more than 6 months a year might be a risk for loosing the green card. There is another way to keep the green card and this is by filing a special application with the immigration asking for a entry permit. This will allow the individual to stay out of the US for 2 years without risking loosing the green card on return. You must consult a lawyer to assist with applying for the entry permit.