Clarification...they are talking about opening the board for next yr in March, not submitting the noms for this yr in March.
Becareful of submitting too early because it could make your packet weaker when compared to people who wait until Sept....this would allow them time to submit higher SAT/ACTs, ECs and more recent grades.
Noms are not given on a rolling basis of 1st come 1st serve. They will not give one nom out until after that deadline date, which is usually in October.
Additionally, you will not know if you are an applicant to any SA until June time frame. Again, the SA's do not do PCQ results on a rolling basis. The person who submits April 1st will find out the exact same time as the person who submits May 15th.
In other words you could be spinning your wheels applying for a nom, and never making the cut from prospective to applicant.