Is there a particular reason to take 6-7 years to build each aircraft carrier?
The US can only afford a limited number of carriers and drawing out the construction time maintains the industry base which is very difficult to get back once you let it die.
The next-generation Ford class aircraft carrier started construction in 2009 and plans to be finished in 2015. The US has capability to finish this ship quicker. Also, what about the technology changes that occur, especially in computer hardware in that timespan of 7 years?
Some of the hardware for the Ford class isn't ready, namely EMALS if they do hurry up construction then you will have a nice nuclear powered barge that can't do its primary mission. Also if they rush through construction what will you have Newport News do until the next carrier is scheduled to start production?
They change hardware less often than you might think. CG-52 was more than 20 years old when they ripped out the ancient UYK-7 computer suite and equally old CIC consoles and replaced it with what is known as ACB08. As long as there are adequate spare parts and the system performs well there is no need to replace the hardware every few years. Especially since installation involves a lengthy ripout, new cables need to be ran (often the length of the ship), then the systems testing and integration is a royal PITA, you also have to retrain the crew which involves flying them out to different parts of the country for schools and team trainers.