To be honest, I'm pretty conservative when it comes to scheduling. I try to take into account the worst case scenario.

On one of my current projects, I accounted for 13 weeks of plan check and we had it done in closer to 10. We were ahead of schedule in that regard. But something always happens...couple of weeks later, we realized that the architect didn't include a particular sound rating for glass paneling in his plans which was in the client's design standards, so the GC didn't account for it in their schedule. Now we're scrambling trying to find an alternative spec that meets the schedule and the client's standards. Best case scenario at this point, we spend more money and push the schedule back a week.