Generally these happen when a storm intensifies so rapidly that the eye from the weaker state can no longer support the new intensity, as such it collapses and a new stronger eye replaces it and the cycle starts all over again. The replacements usually sap 10-20 mph or more off the storm.
However once a storm reaches cat 4-5 and has an eyewall to support that strength, it can enter a steady state and become annular. At that point the only way an eyewall replacement will happen is if something outside influences the intensity and makes it such that the current eyewall cannot sustain itself.
Thanks again. I am glad you are around.