I clocked in around 46 hours. Not skipping dialogue, completing all side missions, earning reputation with squad mates whenever I could, completing all planet scanning and maxing out my war assets. The only thing I did not do was increase my Galactic Readiness (which you increase through MP apparently). Mine stayed at 50%.
Your War Assets and Galactic Readiness do have an impact from what I have read after I beat the game.
Iím armed and Iím drinking. You donít want to listen to advice from me, amigo.