It pays to spend extra time explaining what you’re looking for design-wise in the earliest parts of the process. This investment of time and effort can pay off tremendously down the road.
The more complicated the project the longer it will typically take. If the client is able to clearly communicate their vision for what they want. This includes the look and feel (colors, fonts, images, icons and logos to use) any examples the designer can use inspiration (collages or images that convey the desired aesthetic), then the project could be completed within reason, even rush status.
If for some reason there is a gap in understanding there may be wasted effort by the designer as they won’t be producing the correct look and feel, and work will need to be redone. The less guessing, the better.
On the other hand, the best, more seasoned, designers can take an incomplete or incoherent brief, gaze into a crystal ball and just know what needs to be done. It really comes down to the designer’s ability to work with quick turnaround times as to what you can expect.
Throughout the design process decisions must be made, and feedback given. Some designers work better under pressure and the outcome is just as if there were no time constraints.
Prompt, clear communication can help reduce turnaround times to ensure that good design is produced quickly, and that is the goal of any client/designer relationship.
Personally, I enjoy working under the wire, even if it means burning the midnight oil! There is no time to wallow over if an element in the design should be two clicks below the top line or three clicks to the left. Then there are others that freak out if they don’t have a whole week to create a masterpiece (kidding of course who has a whole week to do that lol!)