In The Tholian Web, when the Tholians show up to bully the Enterprise away, Spock says that they are on a rescue mission and need to wait exactly "one hour and fifty-three minutes" for the Defiant to reappear. Once that very specific time is up and nothing happens, the Tholians open fire.
Why did Spock give such an exact time? Sure that's what he normally does. But he's aware of "The renowned Tholian punctuality", and he's already given the order to not move an inch in case this makes the necessary time fluctuate. He should know that enough though his calculations are correct, it's a very sensitive situation that could easily go wrong in many unpredictable ways. Why not instead claim that he needs "two hours" (about a 5% margin of error), so that if Kirk is even five minutes late everything's still fine? Or really hedge his bets and go for "two hours and fifteen minutes"?