this is a very difficult poll because it is hard to estimate who spends the most time on the front throughout an entire racing calendar.
I always see Knaven on the front, almost every stage, and almost every race he is in. I think he must clock up the most time. Voigt would not be too far off, because he racks up the long s breaks, But those breaks mean someone is still driving the peloton, and Knaven might be one of five riders who are the engines on the front. In this poll that would account for 1/5th of the time.