I would think it would need to be old enough to grow big enough to fit the tube. That is if your talking about the age of the snake. Ha Ha. I have use skins that were tanned for about a week. Just make sure the oil is absorbed and the skin isn't greasy. I have also use skins that were old and brittle. Since I use Elmers Glue to glue the skins I just dampen then with a little water to soften them up and proceed as normal. Good Luck.