On the other hand, good governments tend to be stable under changes in leadership, while bad governments are often unstable when they lose their leader. At least that's true these days, when dictatorships are mostly bad governments and good governments typically take the form of a democracy which regularly changes its leadership with little change to the government.
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.