During Hurricane IRMA I secured my boat with both new 5/8" 3-strand lines and older 5/8" 3-strand lines. The new lines were purchased from WM during one of their sales this year. I had planned to use them on an upcoming cruise we were taking in October. I doubled up all lines from my cleats and the dock cleats. After IRMA passed I returned to my boat I found that 5 of the 6 new lines had broken and only 1 of the older lines had broken. The lines were not mixed in other words new lines were secured together and older used lines were secured together. A surveyor told me that new lines are like new shoes and should be used so they can stretch before using them for a storm, especially a hurricane. Would be interested in your experiences/comments.