Eight and a half minutes is a long time for the same thing over and over. I get what you're trying to do here, it's just that it's a little repettative, using the same instrument the whole time for every single part of the melody. I guess I would suggest a second synth or a trumpet or something...just anything to spice it up a little bit.
Because if you think about it, people's attention spans can't handle 8.5 minutes of anything anymore. So, nice song, good feeling, just needs a bit of a tune-up.