also, we have one of those "fire-ladders" that can be put out of a second floor window to get to the ground -- but it will only work if we practice using them...
While you are at it, why not install automatic sprinklers in every room?
My point is, there is a reasonable amount of precautions to take in the event of a fire. Ladders are an unreasonable precaution. Good, working fire detectors, multiple exits in and out of the house, and taking precautions with day to day use of appliances, candles etc. should be enough.