8 years.

I've got a new proposal. 

We've all noticed that the kind of people who we want to run for president don't run for president very often because getting there, and the job, are both not worth it.  Can you imagine if it was a lifetime deal? No one would run. (Check that, the worst kind of people would run.) 

I don't think it's a huge stretch to say the role of "pastor" is following the same path as president, if it's not there already. 

So, in the same way that presidents can serve a maximum of 8 years, in order to protect both the country and themselves, I propose the church institute a similar policy. You get 8 years as a pastor/leader. To protect both the church and the pastor.