It's intentionally expansive. To be fair, there is always a group of people who find such music boring. It's nothing against either the song or the fan; it's just a fact that longer songs are more likely to eventually becoming boring to someone. That's how the human brain works.
For instance, "Echoes" by Pink Floyd gets a lot of praise, but I find most of it boring. I love "Supper's Ready" by Genesis, but the recent war of epics showed that many here find it boring. Likewise, "Empire of the Clouds" is long enough that, no matter how good it is, some people will find it boring.
I think the key is really paying attention to the lyrics. The music is indeed repetitive at times, but the lyrics paint a vivid picture. This song is like a painting, with a distinct background (music) and foreground (lyrics), more so than any other Maiden song.
I will admit I'm one of those people that just can't get into it. I don't know if it is out of being bored or lack of patience or that I feel it's a little too much for a Maiden record. It's a very unusual thing for them to do and I honestly don't know how I feel about it.
Now, having said that, in no way does it make me feel different about the album overall. It's killer. And I at least appreciate that they were ambitious enough to record EOTC.