There is a complex rotational process that says so many pt hires per ft hire. You would have to literally be "picked' as the one they want out of near obscurity in the right spot on the rotation, and there's always a line of choices for those spots, and they are usually pt mgmt that decides to "go driving". It's a long shot risk to try to hang on while the wheel of hires rotates into position. Plus if you get on as pt and later go ft, all that time counts toward your seniority and retirement, but not so if you just wait it out on the outside.