People do seem to become more entrenched in their opinions with age, but I've often reflected on the fact that given their ages and the dates of discovery of much of the material they taught, many of my college professors must have revised their course curriculums dramatically over the years to reflect changes in scientific knowledge.
It's the only absolutely reliable way of getting rid of bad leaders.
This might not be a good enough reason to oppose longevity tech, but I don't think it's easily disposed of.