I used a parasite cleanse from a website called Keavy's Corner. It had a whole bunch of different herbs in it besides the wormwood, cloves, and black walnut and garlic, which is what Brenda Cosentino recommends, I think. Neem also is good for parasites. The Keavy's Corner one worked for me, but it made me feel awful, so maybe you would be better using Brenda's herbs. But I have no idea if feeling awful just means you are killing parasites.
I think you probably need to do it for one to three months but I could be wrong. I've been taking two or three anti-parasite herbs for over a year now as part of my lyme treatment (cat's claw is good for parasites), but I haven't been doing a cleanse per se. I saw some parasites in the first month or two but not many after that. I'm not sure that I had a very severe case of parasites.
I think it also depends on how strong the parasite cleanse is. I think some of the herbs are not supposed to be taken long-term.
I imagine you could do more than one cleanse at once, but I never did a liver or colon cleanse, so I don't know. I think you could definitely add in milk thistle or dandelion root to anything. Another thing that's good for parasites and candida is diatomaceous earth. It's really cheap, too.