I personally love TFK's epics. The Garden Of Dreams is wonderful, as are most of their others. It is each to his or her own, as usual, when it comes down to it.
For me, I don't care how long or short a song is, as long as it's good. As many people know, I don't think Close To The Edge is all that wonderful, although I do enjoy listening to it sometimes. 'The Gates Of Delirium', or 'Awaken' are better, for me that is.
'Supper's Ready' is probably my favourite epic of all, and is not all that long compared to some.
Also, 'Echoes' is another favourite of mine, better than 'Shine On' to me. Again, as long as I like a song, I don't care about its length too much.
I have heard some Sigur Ros though, and their tracks are far too long! But then, their music sends me to sleep anyway so a two minute song would be too long for my ears! Not my type of thing at all, I'm afraid.