As others have said, this is clearly not what they intended. It adds three days to the original time, not to the days that have been added since. I'm starting to think some people enjoy being overly pedantic!
No!! Not on an RPG forum, never!
Seriously, people. You're perfectly correct in saying that "RAW it takes forever to complete when your PC isn't there", but get over it... every precious ounce of correctness comes of a pound of obnoxiousness. They clearly meant it adds three days to the original time for each of the (originally scheduled) days the PC is gone.
Also, the rules on Carousing are awesome. I love how so many of the "extra" or "RP" mechanics feed back into potential adventure hooks.