When I was in high school, my neighbor at the time had a monogramming business before home monogramming machines became available. Her machines were industrial size. She ordered all her thread from Italy and kept it in the freezer. She had a small chest freezer just for her thread. I don't know if it was frost free (probably not) and the thread was put in the freezer in the boxes it came in. I never asked why, I wasn't interested in sewing at the time.