I honestly think a 20 minute Iron Maiden song would be boring as hell. I'm sure Steve would use a long brooding intro, followed by 5-6 minutes of song, followed by a long brooding bridge that is mostly covered with dialogue samples and cryptic talking, followed by another 5-6 minutes of song, and a fading, brooding outro.
You mean, like this?
I just...what...I can't...I just can't...WHAT IS THIS?! It's a parody, but it's not. It's a cover, but it's not. It's a tribute, but it's not. For some reason, though, I can't stop listening.