Bakemonogatari has 15 episodes. Of course, only 12 aired on TV, with the last three going on the official website over the 6 months after. But the 12th episode was in the middle of a story arc, so it was always intended to be 15.
Finished Durarara, and watched the second season of The World God Only Knows. The second half of Durarara wasn't really that bad. There was about the same amount of Celty, although I was disappointed that the "war" wasn't really fought over Celty's body, as the discussion between Izaya and Shinra's father implied it would be. I suppose her murky affilliation effectively caused it, but still not what I was hoping for.
Second season of The World God Only Knows was good. Slightly more clarification on the background, and they didn't make the mistake of the first season where the final major arc was boring as hell.