Judging by how my naniwa 10k acts, they do darken fast, but if you have enough water happening, it shouldn't start to feel sticky. Keep lots of water going and see how that makes a difference. Also keep in mind that with these high grit water stones you will need to learn the feeling of just surface tension of the water, and the viscosity of any additives (if you are adding a drop of soap or anything) because you can feel that way more with a razor than you can a normal blade.
Are you keeping the blade 90deg to the stone, or are you doing any toe or heel leading strokes, straight or X strokes? How hollow is the razor and how tall (can the space in the hollow be full of water just by surface tension, does the hollow stay dry)?