It really doesn't matter what an academic professor does, or what benefits her union has been able to garner for her. Then again, if a professor in a technical field needs to get some more in depth training, then I suspect time off to do that is fine.
Unfortunately, preachers aren't generally hired to remain on the cutting edge of technical subjects; they get paid to explain in layman's terms something that has been pretty much understood for quite some time now.
But that avoids the question really. Yes, some folks get sabbaticals and yes, mostly in academia. I suspect this thinking is the price we must pay for turning the pastorate into a little academia all its own. The parallels are bound to be drawn.
The fact is though, that most folks don't get sabbaticals, live with just as much stress, and still manage to pay the pastor's salary.
If a pastor is being burned out, I suspect either that she doesn't know how to do her job, or she is refusing to do that job well. Most pastors don't work in construction, or in emergency rooms, or in the military. They read, reflect, and craft and deliver speeches. Some - a dwindling number - actually leave the air conditioned ediface and actually venture into peoples' lives a day or two a week.
Yeah, that's a desk job and it ain't that tough. If it is, we'll hire another one. That ain't tough either.