Less actually. Seven years.
Iron Man, May 2008
Avengers 2, May 2015
I think you could make the case for 'franchise fatigue', especially if the box office figures come down on Cap/Thor(I don't anticipate that myself). Expectations shouldn't be too great for Ant-Man/GotG imo though. But they aren't adding more movies to each Phase, Ethros
makes a good point with condensed timeframe.