A permanent resident needs to not be outside the US for more than 6 months at a time in order not to lose that status. HOwever, keep in mind that it will not work if you plan to be out of the US for 5 months 2 weeks, come back to the US for two weeks and then leave again for another 5 months 2 weeks. After about the 2nd time, your green card will most likely be revoked.