It could take a matter of hours, days weeks even. So, I can't really say I spend X amount of time in designing. There are always alot of factors involved when you're doing layout work... The higher-ups might not be happy with it, you have limited assets to work from, or the theme you're going for is just completely wrong. Sometimes the design you put the least amount of work and thought into is the one that everyone likes. That's just the way it works out sometimes.