As someone who flies AS and UA, I have come to the conclusion that it no 2 individual pilots handle seat belts the same.

Some keep them on until they reach crusing altitude...others turn them off when they get between 15,000 - 20,000 feet.

Some turn them back on the minute they hit a bump...others leave them off until it gets to be fairly choppy.

There is no consistency, just like airports and screening :-)