For playing 1444-1821, 12 hours would mean (12*3600)/(12*377) = 9.55 seconds per game month.
Assuming a pretty early 1700 victory, it goes up a bit to (12*3600)/(12*256) = 14.06 seconds per game month.
That's like speed 3-4 without ever pausing, right?
What's your average play seconds/game month, TMIT?
I haven't measured. I typically do playthroughs in less than 20 hours, but how much less I don't know.
What I do know is that the post I quoted did not say Ryukyu WC, but rather WC at all. Considering people are getting finish dates in the 1600's, I find it very difficult to believe that a skilled player couldn't complete WC in 12 hours of play time with HRE abuse. Even if you lose some optimization to leaving the game running, the cushion is so large.
Keep in mind of course that if you do some game months in 4-5 seconds, you can float 20+ second months also.