[MysticCat]

Not an NPC org obviously, but our national bylaws allow a collegiate member to transfer to alumni membership if the member has paid eight semesters of per capita tax (national dues) or if the member "leaves campus for one or more professional semesters (e.g. student teaching, internship, study abroad)." In the latter instance, the brother is returned to collegiate status upon return to campus. Alumni status means no dues to pay, but it also means reduced ability to participate in the chapter.

FWIW (which I know may not be much).