Presidential noms are non-competitive. They are based solely on whether a parent has the required time in service and everyone who is qualified for one gets one.
Pima is correct re MOCs not selecting on a "rolling basis." However, most if not all MOCs will allow you to augment your files so, if you want to submit them early, there is little downside.
Whatever you do, don't miss the deadline. It is the single, easiest way for MOCs to knock out candidates from the running, especially when they have far more applications than nominations.