Stephenson estimated a good plaster job would last for at least twenty years. Problems of staining, often caused by debris collected in the pool over the winter, can be solved by investing in a pool cover. Plaster is proven material. Of course there are shortcomings to plaster, but the shortcomings don't have to do with the product or application but mainly with the care. The cleaning process is with muriatic acid.
Many people use too much, and the acid eats the surface off the plaster.
Also the pH can be so low in some swimming pools that the water attacks the plaster and eats it up. Stephenson's pet peeve is that more pool managers don't invest in pool covers instead of draining the pool and leaving it to the elements in the off-season. If they were to buy a pool cover and keep on operating during the winter and then not have to drain it completely and clean it every spring and then paint, they'd save money. This is despite the fact that the initial cost of painting a pool is roughly twenty-five percent of what it costs for a new plaster job. Stephenson acknowledged that he's had some good and some bad results with fiberglass.