Algorithm for "pulling/floating" from base unit

I am looking for input on policy related to being pulled from your base unit. I am an RN on a high acuity med-surg telemetry floor. Staffing in our hospital has been poor of late. Our floor has managed to retain a good number of nurses on both day and night shift. Subsequently, we often are used to staff other units.
Does your hospital have a policy? In my mind, the algorithm should be based on continuity of patient care and on fairness to the nurses. I have my own ideas. I'm hoping not to have to reinvent the wheel! Thanks in advance.
The charge nurse has a binder with the dates nurses are floated. We go in order. Nurses with >20 years employment do not float. Lately we've been full census so floating is rare.