Unless we are rewriting how our economy works, the Fed should have a neutral balance sheet, i.e. all the debt it creates by purchasing bonds/securities/etc. should be paid off eventually. Any Treasury securities are going to be paid off by taxpayer money.

If we are entering a new type of economy (which we have been since 2008), and the Fed is no longer worried about having an ever expanding balance sheet, then we are entering modern money theory territory, which is scary to me because we completely lack the oversight needed.