Not IME on DL --- Most captains usually turn it off once the flight levels off. I cannot recall a flight since I moved most of my flying to DL this last year where the sign was on all/most of the flight (without noticeable turbulence). However, on a recent IAH to ORD flight the sign was on the entire ride with not a bump.

There also, notably, was not a single word from the flight deck besides the FAs prepare for departure (no ground welcome, no airborne welcome, and no goodbye). Sometimes I wonder if the seat belt sign is a way for crews to express their feelings toward management (although you'd think the pilots would be fine now).