A report from Black Diamond on the differences in impact forces if you let a rope “rest” between big falls. There is an advantage to this – especially if it is 2 hours or more.
Loosening your knot, or letting the rope rest prior to a fall reduces the impact load on the top piece of gear by a small amount. However, using a different rope for each burn or switching ends of the rope would provide a greater benefit. And of course the best way to keep the forces on the top piece of gear to a minimum is to not fall in the first place.”
Best idea seems to be to switch ends.