I think it depends on how careful you are. If you wash your hands before eating, stay away from animals, stay away from raw fish, etc, etc, etc, you can probably prolong the time between infestations. Generally, cleansing the rest of your organs (colon, kidneys, liver) and making sure your immune system is healthy (through proper nutrition), will also help make you less vulnerable. Parasites tend to infest weaker systems in your body. However, parasites have been around for a long time and I think it is inevitable that you will get reinfested somewhere and at some time. I have a dog and I am sure that she is the cause of some of my infestations, even though I am careful. That is why I feel a regular parasite cleanse is required.