How long do big companies usually give notice after the third round of interviews?

Under normal circumstances, you will be informed within 3 days after the interview, usually not more than one week. If there is no news for a week, you'd better call them and ask about the situation.

Sending qq at night is certainly ok, which shows that you are eager for this job. . . I think they should also understand that there is nothing inappropriate about this.

Of course, it is also possible to send a blessing message. I think they will be happy too. I think your son will come. . Maybe I'll let you know to come to work. .