User blog comment:Deathmanstratos/Some Call of Duty: Advanced Warfare singleplayer background information revealed/@comment-72.197.212.239-20140505030129/@comment-109.148.192.183-20140505104521

They're going to run out eventually, it's better this way because if they concentrate on future/fictional events, it gives more time for historical events to actually happen, meaning more "real history" CoDs.