Instead of constantly looking up at the clock I also use a "audio clock" by that I mean I play "Elected" by Alice Cooper which is about 4:20 long. I have played it so much that I know when the song is about 1/2 way done or getting close to the end. And it has become sort of a subconscious clock where you know exactly how much time you have without looking at the clock.
It works for me!
Dave Conti, RED PLANET BBQ, Ansonia, CT