True story: most of my best received songs have been done really rapidly. Like "Flight" which only took 4 or 5 hours. Kind of insane when I think about it, I have no idea how that happened.
So hey maybe there's something to it. If you're suffering for weeks on a song, maybe that's because there's something wrong with the song itself. (Although I actually liked your recent 2-week-er submission.) I like the chord progression, it is quite sad. The melody needs a bit of work, but then again, it's a 1.5 hour song. I think your melodies in general are improving.