Q. How long does “design” take?
A. Design work can take anywhere between a blink of an eye and eternity.
To formulate better, an idea can come to the designer’s head quickly. Everything else can take time. Online research, actual store visits, browsing through legacy art and competition pictures. Looking for inspiration, looking for trends, for ways to be fresh and cover all client requirements.
In any case, a designer needs some time to realize his or her ideas on the computer and make a decent presentation for the client. That’s a few hours right there :)