Originally Posted by Ricke90
The coincidence really isn't all that incredible. I you think about it for a minute, you'll realize that they all have fired nearly the exact same amount of times. If they are all made nearly the same they will all fail at the same time.
I'm surprised someone didn't tell you to replace them all at once. That being said, replace the rest if you don't want to deal with more misfires.
Replace the other 4 at the same time, so that if you keep the car for another 30k miles, you will know that they all are about the same age. Thats what i would do once they all start misfiring. I will be doing this eventually.