Very good question.
One hopes that by doing FP (say) 2 weeks ahead of scheduled time, he/she will get approved 2 weeks ahead!
Problem is, since approval date is infinite, "infinity - 2 weeks" is still infinity. Besides, we've waited for almost 2 years. What's another 2 weeks...
So yeah, there is no point going early! We can at least save us the anxiety of guessing if the ASC officer will let us in or if "I'll be out of town" lie will work.