I'm in the US, and have had one colonoscopy at age 33 (to rule out cancer, I had rectal bleeding). It was hemorrhoids, but will have another any month now because of family history of polyps and colon cancer. And I'll have one every 5 years even if I have zero symptoms.

You should specify where.

For example in Germany you can get a colonoscopy paid by the health insurance without any specific reason every 5 years from the age of 50. You can always get one at any age for no reason if you simply pay yourself.

Most insurance policies won't cover a colonoscopy without symptoms or family history, and most gastroenterologists won't recommend one in that situation anyways.