You'd be surprised. If you update on impulse, there is a great risk that pacman will break your system. There are clever people who don't update Arch for half a year and then start upgrading it overnight. This is even worse, because the risk of your system dying from an accident increases many times over. Good thing I don't use Arch btw for work. Although no, Arch+dwm is on my old netbook, but I can't find it for a long time.