What is the turnaround time for replacing the battery of iPhone 6s in an Apple Store in California?

Based on its serial number, my iPhone 6s qualifies for free battery replacement due to the infamous unexpected shut down issue. There's no Apple store in my country, so I will give my phone to a friend who will be visiting Las Vegas and California. I guess she will be moving each day to another city, so the turnaround time for this particular issue is really important.

Apple says in general the following for repairs: "Make an appointment at an Apple Store or one of our many Apple authorized service locations, we ll try to fix your iPhone during your visit. In more complex cases, we might need to send it to an Apple Repair Center. If we do, your iPhone will be ready for pickup in 3-5 business days"

So it is either the same day or 3-5 business days. Anybody who has personal experience on the replacement of iPhone 6s battery? If so, how many minutes, hours or days does it take?

I took my iPhone 6S in for the battery replacement. I made an appointment specifically for that, it took an hour.

I did this in Salem, NH though, it might be different in a busier Apple store. I'd recommend going in on a weekday rather than a weekend. The stores are usually less busy during the week.

Depends on the store, how busy they are, and how many repairs are ahead of yours that particular day. If you are lucky, it the replacement gets done while your friend waits for it, and they are in and out in an hour. Otherwise your friend may need to drop the phone off in the morning and pick it up a few hours later or at the end of the day.