Why was Yaakov allowed to leave Eretz Yisroel, and when did he need to return?

There is a third reason one is allowed to leave Eretz Yisroel, and that is for Parnassah. It is then quite interesting that as soon as Yosef was born, Yaakov took the opportunity to “settle up” with Lavan, thereby doing away with the third Heter he had to remain in Chutz La’Aretz. And he was allowed to do it then, because of the Heter of Parnassah.