Hi Carlos, you cannot maintain your permanent resident status if you live outside the United States indefinitely and return only for visits. You must show that your absence from the United States was only temporary. 

If your trip will be longer than a year, it’s a good idea to submit Form I-131 (officially called “Application for Travel Document”) to apply for a re-entry permit. With this permit, you can be admitted into the United States and won’t need to obtain a returning resident visa from the U.S. Embassy. While this document doesn’t guarantee successful admittance into the U.S., it can serve as evidence demonstrating your intent to live permanently in the United States.