I beat the game in 20 hours my first time through. I didn't miss out on much at all. I found a lot of the side areas in the game like say Dr. Gasts place in the snow area. I just play games fast naturally.

My fastest time has got to be around 14 hours. You just have to find the best place to gain a few fast levels to make boss fights go fast and then you can run away from the rest.