Sure it would. In a TT. But you're just talking about practicing in your own course; 15 seconds in practice seems negligible in the real world condition of a race.

Exactly. This is what I meant about beating the guy in front of you. Timing laps in practice seems like a good idea to build up fitness and work toward beating your previous goal, but not that important since it is so dependent on the individual session. I'd be more worried about power output, heart rate or staying upright in practice and finding out what actually works on race day.

I can get behind this.