听说绿卡拿到后即使办了回美证，每年超过半年的话以后入籍会扣除时间，
-It is possible it may disrupt the residency continuity. If staying outside US for > one year continuously, the residency continuity will be disrupted. If the residency continuity is disrupted, you have to wait for another 5 years for the US citizenship application. See this link:
例如五年中累计回国了两年，是否意味着必须等到七年后才能够申请入籍或者申请65岁老人医疗保险？谢谢！
