A 52-year-old current smoker undergoes colonoscopy for screening and is found to have 6 polyps in the ascending, transverse, and descending colon. The polyps are 12 mm, 12 mm, 15 mm, 6 mm, 8 mm, and 5 mm in size. All of them are completely resected. Endoscopic (Figure 1) and photomicrographic (Figure 2) images of a polyp are shown.

Figure 1

Figure 2

At what interval is follow-up colonoscopy recommended?