Colonics are good for quickly removing large amounts of old waste that’s stubbornly stuck itself to the walls of the bowels. Some people carry tens of pounds of this stuff around, and it can take a very long time to remove through diet/supplementation.
If you don’t notice any symptoms of an enlarged colon and don’t have any issues with constipation, you could optionally skip the colonics. There are some drawbacks like the potential of losing beneficial bacteria that inhabit the bowels and other complications.
If you do have bowel issues, colonics could potentially speed up your treatment by regulating your bowel movements and making your bowels more hospitable to friendly strains of bacteria, while at the same time disadvantaging pathogens. A good time would probably be as part of the cleanse. Something like 3-4 sessions within a short period is good for a full cleanse. If you booked a consultation with a therapist, I’m sure they’d guide you through it.