The starting time depends on many factors, including competing obligations and activities.
My son had no interest in visiting any colleges during the application process. He was too busy, he said. And perhaps that was true since he was a debater and spent many hours every day of the week on this during the school year as well as in debate camps during the summer. The only colleges he visited prior to applying were ones where he had debate camps or tournaments, plus my own alma mater which he visited with me on an alumni weekend in summer. He first saw the college that he ultimately attended on “admitted students day,” i.e., after he had already been admitted. He never visited 2 or 3 of the colleges he was admitted to. I don’t recommend this approach, but it worked out just fine for him. Low-key process. I did most of the initial list-making. He did what only he could do – tests, school work, and application essays. The University of Chicago was an excellent fit for him. He had told me “I’d like to attend a college ‘where it’s safe to be a thinker,’ preferably in a major league city” – as in “major league sports.” Chicago filled the bill.
My daughter’s case was different. She definitely wanted to visit colleges, but all on one 2-thousand-mile (round-trip) week-long car trip from the midwest to the East Coast at the end of her junior year. Not an ideal time because she was looking at art colleges and it would be easier to see examples of student art at times when students were still on campus. But this approach accomplished what was needed: meet with an admissions officer, confirm a list of colleges to apply to, determine what was needed in her portfolio, and see the setting or city in which the college was located. She attended RISD.