For me, the best example is Octavarium. When I first heard it, I only liked Intervals. The intro dragged, both Someone Like Him and Medicate were boring, while Full Circle and Razor's Edge failed to engage me. As I listened to it more, it grew on me bit by bit; I soon fell in love with the Full Circle instrumental section and Razor's Edge. The intro followed soon after. Eventually, I came to love each second of the entire track, and it is now top 5 material.
The longer songs tend to take a while to sink in, though I usually come to like them within half a dozen listens. Dream Theater's music grows on me much faster than, let's say, that of Between the Buried and Me or Opeth. No DT song took as long to grow as White Walls or Ghost of Perdition.