I watch the water as an indicator that my blade is making contact properly. I rely more on the "feel" of the edges as honing progresses. As JohnP said it starts to feel like the edge wants to "skin" the hone then it is almost done. The number of laps has varied a lot from razor to razor so I do not count laps and say "done!". I check every 10-25 laps when on the finishing hones.

Just my two cents,