As long as you're not taking up valuable spots where other people need to be there for that year. I don't think it should be a problem. Like you don't want to be the guy who goes to the airport and stands in line in front of everyone who's taking a flight leaving in 5 minutes and his flight is in 2 hours. For this reason you might want to inquire if you should attend during the official campus visit days or outside of those days. But in my opinion I think the earlier the better, it gives you more time to build relationships as long as you're committed to staying on their radar every few months I think that should be fine. With regards to Cornell, I used to live in Ithaca and going your December and January might give you pause

however that is a good middle of the way School between the top ivy ones you mentioned and colleges such as BU, BC, Georgetown.
Farrell Dyan Hehn, MBA
Admissions Consultant & Verbal Strategist MBAPrepCoach.com