I dont think PRL's Have anything to do with your phones Rom performance. Maybe in a rare case it will but not usually. It stands for Preferred Roaming List.The purpose of the PRL is to direct a handset to the best available network to place and receive calls throughout the United States when you are roaming. They change so often because deals with cell company's allowing Sprint/Ect to roam off their towers change. I always update mine when a new PRL comes out. I also do it on my SD card not by calling Sprint.
http://www.corolada.com/prl/