My Vinyl liner was of some undetermined age when we bought the house about 12 years ago (but it appeared pretty new at the time). It began to bleach out around the bottom drain rather quickly, but in general was pretty stable. In the last 2-3 years, it bleached out completely. My chemical regiment has always been the BBB method, using liquid chlorine (the 5-gallon pails from the pool store at 12.5% strength). I pour it either into the pool or the skimmer basket. We never really use that much...3-4 PPM (I use Ben's old test kit).

My PH hovers around 7.2

When it comes time to invest in a new liner due to age, I don't want to repeat any mistakes I made, or is it just natural for a liner to whiten at that age?