I got really board when the had to escape the prison like 10 years ago.
It just became so obvious who had character shields and who was being introduced as a fake main character just to kill and then when they were going to kill off an actual main character.
Unfortunately a problem with the "anyone can die at any moment" theme, like with this or GoT to a similar extent, is that it can only last for so long before you're out of people to kill without sacrificing the overall story arc. So then in spite of themselves, if the show lasts long enough it still ends up with the inexpendable cast on one side and everyone else on the other.