Anytime in the next 6 months. Really.
You could get a letter telling you that your are triple qualified. Admissions likes to call these letters of encouragement.
You may not hear anything until after you have been notified you have a nomination. Appointment wise - most go out in Feb or March from the Congressional nominations.
What should you do now?
You should prepare for your nomination interviews. Continue to do well in school etc.
Keep updating your file with admissions if you win any significiant awards etc.
At the end of your second semester, go ahead and send in your 7th semester transcripts.
If at all possible go online and schedule a candidate visit and take your parents.
One benefit to a candidate visit is the opportunity to sit one on one with an admissions Officer who will review your file with you.
All of this is what I call "showing the love". West Point loves candidates who show interest.
The appointment process is long and arduous. Hang in there!