Auto mode, at least on Boeings, has the seatbelt sign off when both flaps and landing gear are retracted. If either is extended, the sign comes on. We use Auto in flight, when we turn off the sign, so that it will come back on when flaps are extended on the approach if we forget to turn it on.

In years past, it was the No Smoking sign that went off with gear or flap retraction, right after takeoff. Some of us may be old enough to remember that.

As you climb, you climb through different airmasses and the transitions between them often produce turbulence. It is difficult to predict when you'll hit those bumps as your climb gradient is different from other airplanes of different weights or different performance so you end up at the same altitudes at different locations and your experience doesn't match the airplane ahead or being. When level, it's much easier to get accurate reports because the altitude is constant and all you are considering is location.

Early morning flights often have conditions which allow the sign to be turned off early in the climb and I do so when I can.

Most people injured by turbulence are flight attendants. Most injuries occur when the seatbelt sign is on.

Airlines don't release their data on turbulence injuries but they use that data in developing procedures and that is what has driven the change in when the cabin is prepared for landing at United, and now Southwest. I know UAL's numbers because they are included in our training on injury mitigation. I'm sure you know things about your company's business that you can't reveal publicly and the injury data is in that same category. I'll just say that the F/A injury rate was surprisingly high and the data showed that a large number of those injuries were occurring at lower altitudes during the arrival while the seatbelt sign was on and the F/As were preparing the cabin (under 10,000'). Since the change, the rate of those types of injuries has dropped significantly.

The 737 does not have EICAS so there's no indication on the instrument panel when the seatbelt sign is still on. That makes it easy to forget it. For this reason, I run the chronograph when the sign is on. Seeing that sweep second hand running reminds me that the sign is on. It also shows me how long it has been on.

Part of the problem today is that we have so much information on turbulence on our iPads. We have three turbulence forecasting products and four reporting products (including ATC). It is surprising how much disagreement there is between all of those products which are supposed to be showing us the same thing. The result is that we are often flying through areas for which we have conflicting evidence including evidence that there will be turbulence of sufficient magnitude that the sign should be on. In the past, we had old forecasts and only the reports relayed through ATC.

Flight attendants receive technical training in doors, exits, safety equipment, galleys, first aid, and the medical equipment onboard. Beyond that, any technical knowledge they have has been gained through experience or through their personal efforts. I doubt more than a handful know the definitions of the four levels of turbulence or the phases of an arrival or approach. They aren't even allowed to be in the cockpit during takeoff and landing to see what we do. As far as I know, the scripts they read in their announcements were written by inflight managers who, themselves, are flight attendants without specific knowledge of the definition of a final approach segment.