It took Quinneville like three years to make the top 5 longest tenured head coaches in the NHL. A handful of coaches do stick around forever, but NHL GM/owners have very quick trigger fingers with these guys. 19 guys started at their current position in 2013 or more recently. MLB managers don't really do anything. And since very few teams make the playoffs, guys aren't fired just for missing them once, where that happens in the NHL a lot. Any quality organization that misses the playoffs has a great excuse to fire a guy.