回複：簽證上注明1個月探親時間,入關時可以延長至6個月嗎?

The annotation on the visa is only recommondation for custom immigration officer who will give the official stamp for how long your parents could stay. I wrote a letter for my parents to let them to show the immigration office. They got 6-month instead of the 3-month on the annotation. However, someone will tell you if you do this, your parents won't get visa next time. To me, I care this time. If next time they don't get visa, I will write to congressman in my district or state and ask them to send inquiry to embassy or consulate. That's just my personal experience. Do whatever you fell right for yourself