Cultivate early, cultivate often. This doesn't necessarily mean that you need to switch people out every term, but you don't want any individual to be indispensably crucial to the organization, and you want to be ready to pass the baton at any time.

Power is like manure, it only does any good when you spread it around.

Along with what @infuziSporg@hexbear.net said, in my opinion term limits are not the solution to this problem. If the same person is elected for a really long time, then your org is not doing enough to train up the next generation. But if presented with that problem, it doesn’t really help to be forced into electing someone less competent just for bureaucratic reasons. In my opinion. It’s attaining the symptom instead of the cause, in a way that could be harmful.

A thriving org that nurtures new leadership will not have a problem of finding people willing and able to take over periodically

I guess term limits would help with one situation: when Betty from accounting wants to be the Forever Treasurer and will be deeply offended if someone else takes that role. But actually solving that requires org discipline and the strength to tell her that she can’t do that. Using term limits is the passive/avoidant solution in that scenario.