Still most excited about this game than any other this year. Could be partially because it's Doom, or because I have been roaming around in too many open-world games lately (and no sign of stopping, still got Fallout 4 and MGS V to get through at some stage).
So a 13 hr run through a campaign sounds great. I tend to take my time through these as well, savoring the moments and prepping as well as I can for encounters, searching for secrets etc. As long as it's not some 5hr sprint I'm happy.
In any case, I'm not going to buy it at launch price, so still plenty of time to do the math and research once it comes out and see how padded that completion time really is. Anywhere between 9-18 hrs for a single player campaign is quite ok in my books, and a least deciding factor of how much I like a game. If it's that bloody good, just play it again!
This excuse doesn't hold for skimping out on content in multiplayer-only games though.