Greencard has recently been sent to my mailing address in US. However, I currently live in China. My I-131 (travel doc) will expire in November. Do I have to travel back with the valid I-131 to collect my greencard? Can somebody mail or deliver the card to me in China? Once I have the card, can I wait till next year to go to US, still within less than 1 year from the card issuance?