I'm not quite sure time has necessarily anything to do with it so much as being allowed to tell a good story without inference. You've hired good filmmakers, now let them do their job and tell their story.
For example, Sam Raimi made Spider-Man 2
only two years after the first Spider-Man
and he was allowed to make the film he wanted to make. Spider-Man 3
was released three years after the second film but had a lot of studio and producer inference which led to a compromised quality.
While Favreau did voice concerns that he would be unable to make Iron Man 2
in the timetable that Marvel wanted, I think had he been allowed to make the film uninhibited he could have made a better film. Then again, that was probably only one factor in many that contributed to the lackluster quality of Iron Man 2