Abandonment of Residence
By demonstrating intent to abandon residency in the U.S. the USCIS can determine that your permanent residency should be revoked. An exception exists for "alien commuters" who reside outside the U.S. and commuter daily or seasonally to their U.S. employment. If abandonment occurs and any attempt at border explanation to refute such abandonment does not help the situation the only recourse is to proceed again to adjust status. For many people this will again be a very lengthy process. You will be waiting outside the U.S. often with no home, job, health care nor family support.
As a permanent resident you are permitted to only leave the U.S. on a temporary basis. Being away from the U.S. for longer than 6 months raises border agent suspicion that you have abandoned your residency in the U.S. And being away for 1 year will most likely generate a USCIS hearing on the matter.
Play it safe, return before every 6 months, your passport will document this, continue to pay U.S. taxes while away, maintain a home or apartment, don't take foreign employment and don't leave with a 1 way airline ticket.
If you must leave for a longer time such as to care for a sick relative seek a Charleston Immigration attorneys advise to properly protect your green card status before leaving. Remember, "with immigration nothing is as simple as it first appears"℠.
Solution to all this possible stress? Get your citizenship as soon as you are able. Then you can come and go into the U.S. without fear of abandonment reprisals by USCIS.