Liners will eventually leak. Manufacturers have varying warranties, ranging from 15 to 30 years, with a 75-year life expectancy. In reality, it will definitely last as long as the guarantee claims as long as you leave it in the box, and store it in your garage. Once you place it in the ground, nature's forces begin a contest to see which will break its water-tight integrity first. Vying for the title of culprit are gophers, ground squirrels, chipmunks, rats, moles, roots from trees, plants and weeds, sharp rocks, heavy rocks, sharp objects, and moose (if you live in Alaska). If a leak does develop, it is next to impossible to locate it without removing all the rocks covering the liner, draining the pond, spreading the liner out on the ground, and inspecting every square inch. A tiny pin hole can lose five gallons every 24 hours.