Continuing with today's theme of Central Bank balance sheets, below is a visual representation of how the Federal Reserve's balance sheet has changed since operation twist. The chart shows the Fed's treasury holdings broken down by maturity. Notice the hook lower in September for maturities <5 years and the acceleration in holdings of maturities >5 years. In November of 2011 long term holdings began to exceed short term holdings. Total holdings of treasuries have been flat--meaning that QE is not formally in process.
Note that prior to 2008, the Fed held a relatively small percentage of its assets in maturities >5yrs. In fact in 2007 50% of the treasury holdings were in maturities <1 year. Today less than 10% of the treasury portfolio is in t-bills.
I guess if you're going to run a portfolio with lots of duration risk it helps to be the entity that controls interest rates.