Other Employment-Based Greencard/I-140 General Issues

There is no problem with traveling outside the US for less than 6 months in a given year.  If you are outside the US for more than 6 months total in a 12 month period, however, the USCIS may raise issues with respect to whether you have abandoned your green card intention of staying permanently in the US.  They will look at your personal ties to the US to determine your intent to stay in the US.  If they find that you have abandoned your intent to permanently reside in the US, your green card may be revoked.