I'm current at mission 14. I don't know how many days I've been at the steppe (it's been fun:-)
Can I proceed with the story and come back to the steppe later to complete all the missions? Is there any problem with that (i.e., fighting chapter 11 bosses again to come back to the steppe)? I can spend only an hour or so on this game everyday and if I want to complete all the missions before moving on, I'll get out of the steppe in Septermber.