After 180 days you are presumed to have forfeited your permanent residence. After 1 year you forfeit your permanent residence. If you get a reentry permit prior to leaving you can remain outside the US for up to 2 years without any problems.
You should return before 6 months. You should also get a re-entry permit before you leave for some assurance. I agree with Mr. Mark's response.
Please be advised my answers to questions does not constitute legal advise and you should not rely on it, due to the fact that we have never met, I have not been aprised of the facts in you case nor have I reviewed any documents.
There is no definitive rule or automatic revocation of GC. The inquiry will be that of the intent to abandon your residency. Quite a fight, I have to tell you with you carrying the burden of proving that you did not.
I agree with Attorney Segal. Good luck to you.
Dean P. Murray
The Murray Law Firm
560 Sylvan Avenue
Englewood Cliffs, NJ 07632
Mr. Murray's response is NOT legal advice and does NOT create an attorney-client relationship. You should NOT rely on this response. Mr. Murray's response was generated without conducting a full inquiry as would occur during a face to face attorney-client consultation. It is likely that the response above may be made less accurate, or become entirely inaccurate, as you, i.e. the questioner, disclose additional facts that should only be discussed during a private consultation with an attorney. I strongly recommend that you consult an attorney who is licensed to practice law in your state (or, in the case of immigration law, and attorney in ANY state), whereupon all relevant facts will be discussed. All responses posted by Mr. Murray on Avvo.com are intended as general information for the education of the public, and not for any specific individual.
The questions to be address are how long will you be gone, the reasons to stay away, ties to the U.S., etc. to determine whether there are issues of abandoning your residency.
This response is general in nature and cannot be construed as legal advice, given that not enough facts are known. Any comments offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship. If you would like additional information based on this response, please contact my office at 510 657 7665 or 415 902 0832 to schedule a consultation.