You can have a bubble without it bursting right away. You just can't confirm that it is a bubble until that happens. So long as when the bubble does burst, prices drop well below the point at which you were calling a bubble, you would be proven right in the end. A bubble does not have to be at the very peak in order to be a bubble.
By your logic you can call every asset price a bubble.
"The stock market is currently a bubble!" If it takes 10 years for it to fall 30% in one month, you are right it is a bubble, just really, really early. If it falls next week you are right.
In either case, you calling it a bubble added no value.
If you are going to say we are in a bubble, then there must actually be a real bubble at the time, not at some future hypothetical time.
If it took 10 years for it to fall 30% in one month, it would depend on all the activity in between, and where the value ended up relative to the original point at which a bubble was called, in real (inflation adjusted, not nominal) dollars. If there was a complete economic cycle or two during that time, then the original call for a bubble would have been mistaken. However, if it were still the same economic cycle, then that bubble would have been called correctly, regardless if it was 5 years, 10 years, or any length of time. And I was not defining a bubble, I was simply noting that a bubble and a market top are not the same thing.
At any point where prices trend significantly upward, beyond historical cyclical patterns, there is a potential for a bubble. Whether that trend is indicative of a permanent market shift or whether it is a temporary phenomena where prices will revert to the mean afterwards is what decides whether or not there was a bubble. Whether you are at the start of a bubble or near the end of a bubble doesn't change whether or not it's a bubble.
