Unless there is some bug, it depends on your training building level (Barracks, Training ground, Camp), number and levels of your armories and your supporting wonders.
For example my beta queue is around 7 hrs (2 chapters old barracks (I don't have enough resources to upgrade it to current chapter levels), 4 current chapter armories).
And my live city queue (in barracks) is over 15hrs (current chapter barracks, 9 previous chapter armories).
You can get easily to double hours training time if you have many armories or unupgraded barracks (or other training building).