Well, 14 days * 10 hours per day = 140 hours.
Comparing with my own experience, I put approx. 50 hours for Witcher 1, 40 hours for Witcher 2 and, actually, 260 hours for Witcher 3, with a lot of quest missing.
Why not to take your time a little? =)
By the way, after Witcher 3 you can play...