Does my colon need to be cleansed periodically for me to stay in good health?

NO. If you are eating a high fiber diet and drinking 80-100 ounces of caffeine free/alcohol free fluid daily and having regular bm's, then all is working the way it was designed to do. Many colon cleansers are a gimmick and can actually cause damage to the lining cells of the colon.
No. Colon cleansing will remove the normal bacteria in the colon and can lead to overgrowth of harmful bacteria. Stool bulking agents such as fiber, psyllium, or products such as MiraLAX (polyethylene glycol) work to promote natural evacuation of the tract. Probiotics will help maintian the natural flora. A well-balanced diet also will promote normal bowel function.