Thirty threads will probably last a lifetime. These strings look strong and durable but are for emergencies only so I can't rate their effectiveness. You want them to be viable when needed. The problem with sticky strings is that they dry out over time. These strings came in a plastic bag, but it wasn't sealed. Bad idea, except the seller just wants you to buy more regularly. I sealed the bag with wide duct tape and put mine in a heavy duty ziplock plastic bag. I may never need them, but I want them to be reliable when I need them. Then I reckon on mounting them with fresh rubber glue.