Med schools review your app when when it's complete. But they only review it once.
The cycle problems arise because of this. Some schools get >11000 applications (GWU), a lot of people apply early. I remember
LizzyM said that fully 25% of the applications are done within the first month (and this includes 2ºs). Schools only have a finite number of interview spots. If you are one of the first complete applicants you have a better chance to get one of these spots than if you are complete at the end of the cycle when there are fewer open interview spots.
I suspect that the changes to the MCAT administrations (with regard to frequency) will only push that date forward such that an applicant will need to be complete even earlier. They say that there will be MCATs administered in April and possibly June. Well, I think that June date will be very popular and will greatly skew the application cycle. Once test takers finish that exam they will probably concentrate on applications - just like they do now after the August test and after the April results get released.
So, you're at HES, what do the advisors there tell you to do?