I feel as though they just "borrowed" my Bitcoins for 5 days at 0% interest.
Shapeshift doesn't gain anything from this.
Did you enter a Bitcoin Refund Address when you made the transactions? If you did enter one, 5 days is indeed quite long. But if you didn't enter one, and for example deposited from an exchange or casino, you don't want Shapeshift to just return the coins to the sending address.