In Los Angeles, exterior paint rarely fails because of rain. It fails because of sun. UV exposure breaks down the binder in paint, which is why south- and west-facing walls turn chalky and faded years before the shaded sides of the same house.
The first defense is prep. Chalky surfaces need to be washed, loose paint scraped, and bare wood or patched stucco primed. New paint over a chalky or dirty wall doesn't bond well, no matter how good the product is.
Product choice matters too. Quality 100% acrylic exterior paints hold their color and flex with stucco and wood as they heat and cool. Very dark colors absorb more heat and fade faster, so on sunny walls, mid-tones and lighter colors tend to last longer.
Near the coast, add salt air and the morning marine layer. Paint needs a dry surface, so on the Westside it pays to wait for the marine layer to burn off before painting. In the Valley it's the opposite: start early to avoid painting onto walls that are already hot.
If your exterior is chalking, peeling, or cracking, that's the house telling you the paint has done its job. A free estimate is the easiest way to find out what it needs next.