I only sent about 2 to 3 proofs per year to account for my presence the last 5 years. I did so following my parents' application format when they filed for their stuff (we got copies of the packages). The person who helped us out with the application sent in car payment statements from every 6 months with the amount owed obviously decreasing to prove continuous presence in the country. I've read and heard that everyone else is sending monthly stuff, but I figured if they want more proof I can gladly send it in. I included some medical bills, some letters from university professors, letter from a national agency with my certification info, and bank statements of about every 6 months. Good luck! P.S. I dunno how paranoid you are (no offense), so I dunno how comfortable you would be with doing what I did, I know a lot of people wanted to cover every detail possible.