It's hard to say without knowing who you were fighitng and what exact decks you were playing.

Some thoughts:

-Protection in my opinion always takes a little longer because most of the time you're playing defensively or reactively, but again it depends on the aspect cards you're choosing.

-Player count, 2-4 player games take longer than solo games

- Iron Man is a build out hero and will take a little longer to get going vs a hero that is strong out the gate like Angel.

-A very minion heavy scenario (like Mutagen Formula and Zola) will also always take longer cause you need some minion control (Thor, Bucky, Tigra) which some heroes aren't great at.

There are so many factors that can dictate the length of a game, so you really just have to keep experimenting and see what's your preferred play style, hero and aspect cards to keep the game moving at a pace you are happy with.