You dont need to replace them with every brake job. Only when they fail. Just like it says you need an oil change every 3k miles. Unless its got high miles or your in extreme weather conditions, its safe to go over 3k. Just dont let that turn into 10k like my friends sister. But ya, you might want to replace them instead of ghetto-rigging it. You'll regret it in the end. And replace only the ones worn out.