Saying the Federal Reserve has "printed $415 billion" without qualification is dishonest. It has created $415 billion worth of liquidity for short-term operations of solvent banks, essentially printing money and then destroying it the next day. It has not added $415 billion to the money circulation.
There are two separate things going on here; although both of them intended to relieve pressure in the money markets.
Firstly, there's a so-called "reserve management operation" which is intended to increase reserves held at the Fed by purchasing Treasury bills. Increases in reserves implies greater liquidity to support money market activities. This definitely shows up as a growth in the Fed balance sheet, as the policy is to roll into new Treasury bills at maturity.
Secondly, there's an ongoing campaign of overnight and term repo operations where necessary to achieve the policy target rates. These are short-term, and do not result in a significant balance sheet growth.
Your statement was a lie of omission. They printed a much smaller amount, destroyed it shortly afterward, and then repeated that on several occasions until the total amount was about $415 billion. A reasonable person reading "the Federal Reserve has printed $415 billion since mid-September" would take it to mean that $415 billion was added to the monetary supply, which is not what happened. You're disingenuously leaning on how your words will be misinterpreted to stir up unwarranted hysteria about inflation and whatnot.
Nothing was "destroyed". Rather, it was rolled over for bidding the next day (or 14 days, depending on the specific operation). It's an important distinction, because until the actual FRB balance sheet unwinds back to the $3.76T level it was in September, it is precisely as OP describes.
The delta of the FRB's balance sheet between Sept and now is 4066-3761 == 305B. It's not 415B, but it's not even remotely close to 0, either. During this period, there has only been a single weekly draw-down. All other weeks have been accumulative, and should be considered QE4 unless and until these operations stop occurring.
