Here in the Pacific North-West, Miller Paint is one of the prominent regional companies that make very good products.
When I moved in my present house going on 9 years ago, I painted one coat of their flat housepaint over the builder's paint on the Hardi-Plank siding. Granted, Hardi is great at holding paint, but after several years it still looks great. This year I was thinking that maybe it was time for a maintenance coat, but after powerwashing, I asked myself "why"? It still looks great!