I'm glad someone else already pointed this out, but isn't 10-15 years about RIGHT for a liner???
What's so strange about that? I don't understand why your pool guy didn't just chalk it up to typical age-related wear & tear on your liner.
When I was researching various pool types before we built ours, I was told several times that a liner only lasts about 10-12 years. Indeed, it was my primary reason for deciding to go with gunite.
Just my .02