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 8老师，感谢您一直以来的支持，今天终于拿到IV签证了，真心的非常感谢。

       我拿到的签证有效期到4月中旬，和体检有效期半年正好是一致的。我现在还有一个问题请教您，请问您我入境后是必须一直在美国待够时间（比如1年？）？我听说是入境一段时间，然后可以回国待一段时间处理国内事情，然后彻底去美国，但是这样的话我从中国再去美国时，IV签证就过期了。请问您入境后在美国的时间是什么要求？谢谢您
-When you enter US using the immigrant visa, the IO at the port of entry will stamp/endorse the visa on your passport. Thus, you become a green card holder immediately. The stamped (endorsed) visa is equal to the temporary green card which is valid for one year. USCIS will send the plastic green card to you after you pay the immigrant fee. If you leave US any time before you get the plastic green card, you use the stamped (endorsed) visa to come back to US. 
See these websites for the immigrant fee payment:
https://www.uscis.gov/forms/uscis-immigrant-fee

https://my.uscis.gov/uscis-immigrant-fee/