Vinyl liners, obviously, are more fragile than solid liners and subject to puncture. Some installation processes use sand instead of the concrete mixture on the floor, with a layer of wall foam beneath. However, roots from nearby trees or other vegetation can actually grow through the liner.
Pool maintenance tools and pets can also cause accidental puncture if precautions are not taken. In addition, liners can break down from pool water and sunlight over time, making the liner brittle and prone to cracking in stress areas. And bacteria can cause discoloration in a liner.
Under perfect conditions, the life expectancy of a middle-range quality liner is about 6-years; longer for higher-end liners.
Plus having worked on several this season ,all with the same problems (punctures) im just glad i took the Real pool option ....as with all things in life you only get what you pay for.