Actually, I think it can be shortened down. Unless you're taking a trip. But the pace is kind of uneven and interrupted with some of the tracks. Try making a "best of SMiLE" playlist and you will find a great great great, shorter album.
Btw, @metawirt, being a Pet Sounds MANIAC, I must advice you to give it another chance. There is no way anyone could be disappointed with that album, since it is ethereal. No - sorry, it has nothing to do with taste. It's just a fact. I would never say that about any other piece of music, I do really believe that people have different taste and I actually respect that usually, but NOT when it comes to Pet Sounds! Because I was disappointed first too, but now it is the love of my life. You just have to keep trying. Realize your own limitations and broaden your musical horizons.