To win the war another time, I guess ? To be fair, he told us we would get "tired of winning".

On a more serious note : could it be that iranian air defense is being supplemented by an ally ? Someone further east ?

Or, simply, that they kept some reserve to keep the war long, and play with the American customer's never ?

Iran has been preparing for this for decades. I wouldn't be surprised if they held a hidden reserve for air defense and let the USAF 'get comfortable' before redeploying