I'll echo what mmc51264 said. I've been at my current employer for 6 years. There's not much happening above me on the seniority list. Every now and then someone retires, or decides to go to the outpatient 9-5 pm life, or graduates from grad school. For the most part though, those nurses have enough seniority that they are getting the schedules, holidays, and vacations they want.
On the other end of the spectrum, new hires are required to stay on the hiring floor for 18 months if they want to continue working for my employer. So needless to say, no movement there. The challenge is keeping nurses invested and engaged between the 18 month and 5 year mark (at least in my experience).
I'll never say no to pay increases, respect, or pizza though!