For 4x4x4, definitely work on your lookahead during edge pairing. You had way too many pauses and the pauses took up too much time. I noticed that you rotate the cube while searching for edges to pair. However, I find that holding the cube in one position during the entire edge pairing process helps me find edges quicker, because the the cube is steadier.
Also, for 5x5x5, you waited 7 seconds between centers and edges, while you kept rotating the cube, so that advice applies for that cube as well.