Took about six to seven months, playing every week for 5-6 hours per session. Didn't miss many sessions (maybe 2 or 3 total) and there wasn't much side tracking or lengthy discussions. Book 5 was a bit of a problem as the party went straight for the info (by pure dumb luck) and had to trudge through the rest of the book to get enough xp to "move on". They by-passed much of the "filler" in book 6.
** spoiler omitted **
The final battle was pretty epic, though.
This is part of the reason we agreed to ditch XP altogether and hand out levels upon reaching certain plot points. My group only hit 3 wings of Runeforge and immediately split, and this was after I made the place inescapable via any means other than the one in Wrath. They'll probaby try to run straight up the mountain, but that occluding field will likely send them back to the lower city for a while.