The short and crisp answer to the question is “no one knows”. As the old saying goes—predictions are hard, especially about the future. It’s hard to know when the bubble will end. It’s impossible to know if the price will keep going up, and it’s hard to even guess. We also have no idea if going “short” right now, or betting that the price will decline, will be better than going “long,” or betting that the price will continue to go up over time. Again, Bitcoin is highly volatile, and is thus not a conservative way to build something as essential as retirement. Bitcoin and other crypto currencies are so new that the market is still essentially trying to figure out their value. We don’t know what it’ll be like next week, never mind when you near retirement age. Catalini compares what’s happening now with Bitcoin to people wondering about the “value of the equity in a startup.” As expectations about the future potential of a startup shift, the perceived value of that startup changes too, and can fluctuate wildly. Something similar is happening here. However, according the positive speculations “anytime” is right time to invest in Bitcoins.