a show like this would be considered ideal, because it was highly rated, so you might feel some sense of job security (relatively) for a while, especially if you are between seasons, on a hit show you know is coming back, and there's really no reason to think that would change, so you'd feel comfortable say, dropping a down payment on a new car, or adding on to the house, knowing you're good for another year at least.

once a show ends, or get cancelled you are essentially fired. i work in post, so i'm not sure exactly how it goes down, but i believe you put your name back out there listing yourself as available, and different productions/production companies will chose you based on your rep, who you know, etc..

a big show like this, much of this crew has probably worked together before, many of them may be fine, but it still really sucks and is something that can throw a huge monkey wrench into your life.