you can't expell those that are living within the body's subcutaneous tissue/fat, they are not going to move after treatment conveniently towards the intestine, colon, nose, throat or any other orifice
The cells will try to eliminate the foreign materials, there are the blood and lymph networks designed just for that.
If you believe that dead worms or their waste stay in your body, you'll be already dead.
And yes the die off symptoms are more important when there are more dead worms or waste to eliminate.
But i agree with you, several treatments should be done regularly in order to kill the remaining larvaes.