WI: No Byzantine-Persian War 602-628

While researching Persian military formations, I got into reading about the Byzantine-Persian wars. It was all epic, especially the last one which read like a legend with the hero riding to the rescue just when all seems lost and driving deep into the enemy's heartland. But it devastated both empires mere decades before having to face the Arab invasions.
So the question is, how would both sides be able to weather the Arabs and other threats by either avoiding the war or by significantly shortening it? Could the Arabs and Slavs be contained and kept from entering the Empires? Could it help both empires avoid collapse and even heal tensions with a new, dangerous rival appearing? Would the Byzatines be able to reconquer the Weet without the Persian distraction?
 
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