Unless the Prez (or something else) reins them in , I am supremely confident the fed can buy an unlimited number treasures and keep rates exactly where they want.
(Inflation is an entirely different matter however),
NOTE:
They print the money, they return every dime profit back to the U.S. treasury once everyyear.
There are very few Gov’s out there that can do that, we can “BECAUSE WE DON’T REALLY NEED ANYONE ELSE, THEY NEED US A LOT MORE THAN WE NEED THEM”
At least for now.