Silk will last forever. I am using some they sewed parachutes with in WW1. The rayon also will last. The little ones are pre-wound bobbins. I use these in my FW and my Janome. They are wonderful as they use to make them with very fine but stronger thread. The varigated threads are not very old so you should not have a problem with those. WOW! Just like Christmas only better for a quilter. To use the bobbins in a FW you pull off the front and back gently and put into the bobbin holder. I love them. Saves me so much time.