Possibility of a Very Extended Period of Low Rates?

We've heard the Fed continue to say they intend to keep exceptionally low rates for an extended period. How long should we expect rates to remain at these rock-bottom levels? This blog post at BankFox has a good summary of economic conditions that could lengthen this extended period, and it warns of a worst-case extended period:

We shouldn’t even be surprised if our rates are low for years - after all, Japan has seen interest rates below 1% for more than 10 years since its economy stalled in the 90s.