In the world of positives and negatives, people who decide to take on these sacrificial lamb jobs always know that the benefits of even holding the job for any length of time outweigh the negatives that come from this job. That is how it is in politics. You work for a personality and you have to do that persons bidding. 

And as with any administration's personnel, there comes a time for each of them where the benefits are not enough to outweigh the negatives. It is at that point where you see people like Spicer, Preibus and even Conway pull up stakes and move onto the next gig. 

That is the way the rules work for political appointments, nicely stated by the good professor.