American green card exit time limit

Generally speaking, green card holders can not live in the United States for less than 6 months each year. Try not to go abroad for more than three months at a time. If it's more than three months, the immigration officers will ask when you will return to the United States, and they will pay attention to you. But it doesn't matter much, as long as they know what to do and why it takes so long, they don't care. One suggestion: If your father needs to live in China for a long time, he should apply for a re-entry permit from the US Immigration Service. This re-entry permit is valid for 2 years, so as long as you return to the United States within the validity period, there is no problem.