How long does it take the Mumbai Consulate to schedule a K3 interview once it receives the application files from NVC?

It depends on what time of the month your file reaches Mumbai. If it reaches Mumbai a few days before the 15th, you should expect a date for next month. If it doesn't reach Mumbai by the 15th then you're looking at the following month.

For instance if your file is already there by today you can expect a date in November if it's not there yet then you're looking at a December date.

It also oppions when you get packet 3 mail off to them... and when you get packet 4! GOod luck to you did you get everything you need?