The general rule is that a Green Card holder should not spend more than six months out of the U.S. in a year without first obtaining a re-entry permit. That said, the primary consideration is whether the Green Card holder can prove his/her intent to reside in the U.S. Prolonged absences can be perceived as the abandonment of permanent resident status. Green Card holders traveling abroad should maintain strong ties to the U.S., which can be demonstrated through home ownership, employment, the presence of family, school attendance, bank accounts, tax documents, etc.