QE has helped prevent a 2nd Great Depression and where is all the hyperinflation that was promised ? Of course there are limits as eventually endless printing of money will bring hyper-inflation but I think Bernanke has a good handle on where the limit is.
The economy appears to be recovering on its own now and all those QE bonds can be sold and the money recouped made to disappear if inflation is a problem again. The point is that a lot of the money that went into stocks disappeared in the 2008 crash so money disappears out of the system too as well as just being created by QE. It's a balancing act.