Generally speaking...there are exceptions...the more competitive the program, the earlier the recruiting process starts. A few rising juniors have already committed.
After the top conferences skim off the cream, the mid-majors go after what is left, and so on. I do not have current stats, but signing "early" is now the norm with more than 60% (70%?) of commitments inked then.
This creates a risk in waiting since most slots and money will have been allocated in November. The elite can afford to wait if they wish, of course, there will always be slots for them. But for those suffering the "four-star blues", November is becoming the target date of necessity, I think