I used the eco-earth for a short time. Before you put it in the enclosure you need to dry it out. There are a few problems overly moist substrate can cause.

If you would look around the forum, 90% humidity is FAR too much and yes even for just a week it can be harmful to the snake.

As everyone else has stated, I recommend using aspen. I went from eco-earth to aspen and I will never look back.