KA, forgive my lack of recollection at the moment, I will post again later when I find the name, etc, but my favorite symphony/ opera was five hours and there was this chord(?) that just kept coming out, er, "wrong" to the ear, like, the human ear doesn't expect it, ya know? And anyway, this built up tension internally, just listening to it come out wrong again and again, until, finally, in the fifth hour, the right chord was hit and all the tension just melted away. I know, you probably have no idea to which I am referring, but I sat through that twice because it was so, well, orgasmic, for lack of a better term. I'll find the name of it and the composer. Perhaps you can be inspired by it.
Also, when all else fails, Wagner. The man is a god.