I had previously played Ego Draconis, so playing DKS took me 39 hours for the first part, and another 17 for the expansion, so 58 hours.
That was only doing about half the content though, because of the alternate quest solutions all over, so I would say that over 100 hours of content is correct, even if you need to play it twice. I've finished DKS 3 times now, a total time of 170 hours.
