This is my experience, but I have only been cleansing for 15 months with limited drugs/herbal remedies.
I expect some parasites are more difficult to shift.
I have tried dosing myself with herbs for 5 months on a rotation basis
Artemesia with black wlanut, cloves, quassia etc.
Olive leaf, pumpkin, cayenne, garlic.
I have also had 7 doses of Ivermectin -drug.
In my opinion 3 weeks of herbs is as effective as one dose of Ivermectin. all killed, but none got rid of them completely, so when I stoppoed treatment they slowly came back. I believe I will have to stay on maintenance for life.
Having used both, I am pleasantly surprised with just how effective the herbs are. I think they are probably safer for long term use.
My problem is strongyloides which is notoriously difficult to completely cure. they say it is a disease for life.