You've mentioned that you mostly write music from beginning to end.  Does it ever happen that you come up with a tune or lyric, and as the song comes out, you realize you want to shuffle it around a bit, or do things generally stay in the order they appeared in?
often i will be bombarded by ideas that would go much better the second or 9th or 101th time through that section. for example if i have a verse melody, i always get bombarded by things that would work super great in the 57th verse. of course i'll write them all down, but only time will tell whether that actually works or comes up again when the 57th verse rolls around. and it won't, because the song would surely be over by then, unless it's one of those non-ending songs