If they wrote the album with the idea of making it double, then it must be a first in DT history.
As far as I know, before DT12, they had never planned album lenghts, they just worked until they could do no more. On DT12 they made it (relatively) short on purpose, so I can assume that they aimed at making this huge double-cd opus. With this, we can get to the conclusion that Act I and II indeed represent CD1 and CD2 respectively (The presence of Overtures on each of them confirm this).
Vulgaris and Pax's math seems to be extremely accurate, and even if Noxon had indeed messed with the values, that doesn't change the product, the order doesn't affect the result, you'll still find out that no song exceeds 10 mins, or so it seems.
Awesome work guys, thanks.