all the time, they take like half of the episode to transform, and after that, in the same fight, they transform in 1 second. This benefits the gamepleay because after you transform for the very first time, if you run out of ki, you shouldn't wait that long again to transform. Watch the show, man, 2 examples: the battle against freezer, the first transf lasts like 5 minutes, and the second one, near the end, 2 seconds. In the battle against cell, te trans. of gohan to ssj2 lasts a couple minutes, and after cell explodes, gohan transforms instantly, thats because he's "warmed up"