There are certain presumptions, that is, being outside the U.S. for at least 6 months or 1 year, that can cause problems but if these presumptions aren't trigge

There are certain presumptions, that is, being outside the U.S. for at least 6 months or 1 year, that can cause problems but if these presumptions aren't triggered, the analysis focuses on intent: is your stay outside the U.S. temporary and is your intent for the U.S. to continue to be your permanent place of abode. If it is likely that you will be outside the U.S. for more than 6 months, then you should get a reentry permit (which is applied for using USCIS Form I-131).