As a mother and guardian with American children, how long can I stay in China with a green card and a return permit? Is there any way to postpone it at will?

Your child is American, you have no privilege!

You have a green card and are free to enter and leave the United States, but you must stay in the United States every year 180 days.

If you have special circumstances, you must apply for re-entry permit nine weeks before you leave the United States, but that is not permanent.

Just once,

If you go on like this, your green card will soon be invalid!

You think so beautifully that you can't wait to take advantage of all the advantages in the world!

But the truth is not what you think!

It seems that you are speculating about the US Immigration Service with the idea that China has strength and wealth.

Then you are all wet!