Sometimes bosses can drag on a bit. The final boss of Persona 3 was too long for me, though I was fairly underpowered by that point. The only thing that kept me from being bored was the epic music playing.

And I'm always scared to go all out on a boss at first too, making it even longer. It's all the rage to give the boss a dozen transformations and all. Sometimes it doesn't happen and I end up smacking myself for withholding.