Better Homes and Gardens has some good painting tips.
Spend More for Quality Paint
The accrued costs of frequent repainting cancel the “savings” you enjoy by buying the cheap stuff. Good-quality paints cost more because they have a higher percentage of titanium dioxide, which determines covering ability, and other additives that increase durability. The heavier bodies of high-end paints help them go on smoother, splatter less, and resist fading.