K trains that come late

I need to take two K rides from Chengdu to Yichang and from Yichang to Zhangjiajie. When doing transfer there is a gap of 2 hours. I thought that should be enough to get off from first one and get in other one. However a Chinese colleague strongly indicating to change the first K ride with a D type, saying that K type usually came very late and 2 hours will be not enough for transfer and that there is a high probability that I will lose my second trip. If they are late, why is is not indicated anywhere such information? Why when making the time tables for tourist is not presented info on the late venue and how much late in can be?