If warp wins and consumes everything then it stops to exist. They live from emotion and if there is no one to live in our universe then they cannot get their power
Usually after a war countries experience a surge in economic growth, because all these people that were doing war or producing war equipment can now start doing something productive. For some time then it is time for peace.
Ok, i know this is all fictional. Yet, if the model of the Emperium is solid, the Chapter Masters when they learn art, poetry, battle tactics...just like the IDEAL ROMAN VETERAN...farming, local government, morale building - schools, universities. I know it's a UTOPIAN IDEAL...Warhammer has it's foundation in Ancient Rome, so in art and literature - MAKE AN IDEAL, REAL!!!
What Would Happen If Each Faction Won - Warhammer 40K Lore
Thank you