Board Thread:Shingeki no Kyojin Manga/@comment-24930713-20150609084033/@comment-5774380-20150609221022

The second season is taking so long because of the monthly format of the manga. They can't release a season every year, for example, because 12 chapters are not enough to complete an entire season unless you make up a lot of filler episodes. That's why they have to wait several years to gather enough material. :/