In general that is not an issue unless someone is in the process of naturalizing, but many people still apply for a re-entry permit with this planned timeframe as plans often change, so 6 months can easily be extended past 12 months. As you can see from the USCIS website below, nothing is cut and dried.
Good Luck!
Permanent residents are free to travel outside the United States, and temporary or brief travel usually does not affect your permanent resident status. If it is determined, however, that you did not intend to make the United States your permanent home, you will be found to have abandoned your permanent resident status. A general guide used is whether you have been absent from the United States for more than a year. Abandonment may be found to occur in trips of less than a year where it is believed you did not intend to make the United States your permanent residence. While brief trips abroad generally are not problematic, the officer may consider criteria such as whether your intention was to visit abroad only temporarily, whether you maintained U.S. family and community ties, maintained U.S employment, filed U.S. income taxes as a resident, or otherwise established your intention to return to the United States as your permanent home. Other factors that may be considered include whether you maintained a U.S. mailing address, kept U.S. bank accounts and a valid U.S. driver’s license, own property or run a business in the United States, or any other evidence that supports the temporary nature of your absence.
https://www.uscis.gov/green-card/after-we-grant-your-green-card/international-travel-as-a-permanent-resident