I told my LOR providers that I needed letters for 5 schools, even though I never actually intended to apply to the 5th one. I asked all of my letter providers to write paper rec letters, and sign and seal across the back of the envelope. I opened the letter from one professor (the other profs let me read the letters they wrote) for the 5th school. Nothing bad, but not wonderful either. So, I asked another professor to write a LOR. Most schools will let you gather all of your LORs and mail them in one packet--as long as they are signed across the seal.