There are definitely benefits to being hired on as a full time and permanent project manager. Job security, obviously, is one of them. Being able to really bond with your team as you move from project to project within a company is also great (provided you like everybody). At the same time, because of the nature of the work, finding a permanent/full time gig is rare. So what do you do in the meantime? Do you just allow a series of layoffs to hang out on your resume while you scour job boards and volunteer, living off of your severance pay or unemployment? This is certainly one approach.