Seeing as how you would only run the VoG up to the Gorgon CP and Crota up to the Deathsinger once, I can see three hours max. How and what am I talking about? You don't run both raids three times. You run them once and switch characters at the Gorgon and Deathsinger CPs so that when you go to run your second and third characters they are already starting at the CPs.