AIUI, creosote doesn't prevent rot, it merely deters it, that is, slows it down or delays it (and not as well as arsenic products).
So what about railroad ties.
They seem to last for 50 or 100 years or more. Do they have to be replaced because of rot? All of them? If not all of them, does that mean that the creosote stopped them from rotting?
Or do they replace them all, when I'm not looking?
If they last for 100 years when used for railroad ties, how come they don't last that long when used to support decks, etc.?