请问B2签证回国后多久可以再去签
我父母去年B2签证来美，9月中旬回中国，共住了7个月10天。 期间我们申请了B2 延期，去年10月下旬批准。
现在我又想尽快请父母再申请B2。
请问各位见多识广者，什么时候再去签B2，签过的把握性大？
曾经听说B2 申请人在中国居住应比在美居住时间长。不知此传闻正确否？请分享正反面例子。
谢谢！
PS: Their last B2 visas expires by the end of this month. So they will be eligible for renewal without interview. But it is said they still need to go to US embassy to get finger prints taken. Is an appointment needed for finger-printing alone? Does anyone know?
Thanks!!