Read carefully the following, and also read that link page too
http://uscis.gov/graphics/howdoi/permres.htm
Good LUck and keep pass the info.
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Permanent residence is not the same as citizenship. Permanent residents of the US remain nationals of their home country. They do not hold US passports and they do not owe allegiance to the US. They may not vote in elections and they may not hold elective office. After a certain period of physical presence in the US (five years in most cases, three in some), permanent residents can apply for US citizenship if they choose, but it is not necessary to become a citizen to retain the right of permanent residence.
Maintaining Permanent Residence
Maintaining Permanent Residence You may lose your permanent residence status if you commit an act that makes you removable from the United States under the law in section 237 of the Immigration and Nationality Act. If you commit such an act, you may be brought before the immigration courts to determine your right to remain a Permanent Resident.
You may be found to have abandoned your permanent resident status if you:
Move to another country intending to live there permanently.
Remain outside of the US for more than one year without obtaining a reentry permit or returning resident visa. However in determining whether your status has been abandoned any length of absence from the US may be considered, even if it is less than one year.
Remain outside of the US for more than two years after issuance of a reentry permit without obtaining a returning resident visa. However in determining whether your status has been abandoned any length of absence from the US may be considered, even if it is less than one year.
Fail to file income tax returns while living outside of the US for any period.
Declare yourself a “nonimmigrant” on your tax returns.
Change of Address
You are required to notify us of any change of address within 10 days of that change. Form AR-11 is used for that purpose. You can learn more about change of address requirements is found at "How Do I Report a Change of Address?"
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Good Luck