Interesting question, and different philosopys. Humaworm says to stop inbetween for 90 days. Sutter says Never stop killing. I had to go with Sutter's because after my humaworm round, I felt itching and movement. I couldn't let them keep reproducting. I had stopped for 3 weeks, then decided I had to get on Barefoots's DeWormer. What a relief. Now I've been on that for about 3 months, and am thinking I need to rotate everything. IT's hard to know.