I guess its a good idea to keep a couple, and if there was any kind of water getting into the panel, I would push for a panel change as a minimum, and possibly a service upgrade. I have to admit, I have had very few calls, where a FPE breaker was bad. Usually, I would see the whole panel burn up. I allways tell the owner, that these breakers are known not to trip. Usually the people will listen. There's nothing like seeing a home owners panel box, and there it is, and you say to yourself, I feel sorry for this guy.