When they make iPhones it usually takes about a year. But the iPhone has to have 1 thing new to it and that's where the 10 to 3 to 1 process comes in...
...The 10 to 3 to 1 process is where Apple comes up with 10 entirely different ideas and then pick 3 of the best and then pick 1 new thing to add to the new iPhone, then they test the new iPhone.