I'd agree that the key to a properly-executed epic song is to make it seem like you HAVEN'T been sitting there for ten minutes plus, to get you so wrapped up in the track that you get lost in it and don't realise how much time is gone by, and indeed you're wishing there was more!
Some epics can get VERY tedious. My own experience of that would be the l ikes of "Harvest of souls" by IQ and "Sweet hope suite" by Salem Hill. Both tracks I really TRIED to listen to, but basically my mind wandered and in fact I think I fell asleep during the IQ one!
Proper epics I would list:-
Marillion --- Grendel
Genesis --- Supper's ready
It Bites --- Once around the world
Mostly Autumn --- The spirit of autumn past
Fish --- Plague of ghosts
Meat Loaf --- Bat out of Hell
Marillion --- This strange engine
Dire Straits --- Telegraph Road
ELO --- Concerto for a rainy day
Supertramp --- Fool's overture
Iron Maiden --- The rime of the Ancient Mariner
Kamelot --- Memento mori
I'm not sure if they're all over 10 mins, but some great trax there!
I may be back with more...
