I put a rubber one on a Bear Kodiak, back in the late 1950's while in school, left it on except to change a string. It was on when the lower limb delaminated. Since I bought it from Glenn St. Charles, I took it back. Bear gave me a replacement bow, and Glenn told me not to use one, unless I was willing to take it off and put on when going out to shoot. He said, they can hold moisture and dirt which can cause problems. Never used one again.
I like the dental floss idea and have used it to make the loop smaller, especially useful on longbows with small nocks.