Besides applying two coats satisfies the warranty, it also extends the paint job’s life for years.
For example, the picture on the right clearly shows where someone brushed the edges and seams and then painted the exterior wall with a roller.
The areas that received two coats have significantly more paint left.
Applying a second coat of paint usually adds about 30-35% to the total cost of the job. Considering it can extend the paint job’s life by 5 years, it is a wise investment.
It is not always necessary or recommended to apply two coats. For example, areas that get little or no direct sunlight and are protected from rain often need just one coat of paint.