Great question. In the 2021-22 cycle, I received a II on 12/05/2021 (a SUNDAY, no less). In the 2020-21 SDN forum, I heard of people interviewing in February. Therefore, I don't believe they're done sending interview invites. All decisions are made before or by 11:59 PM on March 15th, so, if the 1-month minimum response time stands, theoretically the last month to receive an invitation would be mid-February.
However, they're interviewing 400 people this year instead of 500 people like last year, so this timeline could have changed. It's hard to tell.