It depends on your program, and the doctors schedule. As soon as I got to my goal weight, I called, but then I had to get a CPAP machine, so that prolonged it a bit. But as soon as I got that, I had a date little over two weeks out!
I was very surprised that my insurance approved the procedure about a week after it was sent in. I was expecting it to take a month. It took a few more weeks to get a date that worked with the surgeon. It was worth the wait!
It depends about how efficient the doctor's office staff is, and how persistent you are. I waited a month after they said they filed insurance only to be told they needed approval from my PCP (which was completed months before). Then when they actually filed, it took 2 weeks to the day to get insurance approval. But then they told me I had to pay my co-pay before they could schedule. So I had to wait another couple of weeks before I had the money.
But I was not aggressive about calling and getting all the information I needed.
I had the same trouble with my Dr.'s office. I thought I had all the paperwork in and was just waiting approval. It turns out it sat for 2 weeks because they were waiting for approval from an allergist because of a bad reaction I had once to a particular medicine--turned out NOT to be an allergic reaction, but all that had to be documented and nobody informed me what was needed. I got them the proper forms, and my surgery was approved less than a week after being submitted.
My doctor set my surgery for 3 months out to give the insurance company enough time to approve it, go through the 3 visits with a nutritionist - each a month apart - and have time for a psych eval, all of which is required by the insurance company.