Regarding Santiago, there is a procedure requiring flight crew to switch the signs on 40 minutes before landing, and leave them on 30 minutes after takeoff, due to the possibility of severe turbulence over the Andes (I’m sure one of our resident flight crew will confirm). There are certain other regions where seat belt signs are required to be switched on at certain points, but these are procedures related to the security requirements of certain countries.

On shorthaul, it’s generally when flight crew agree it is safe and appropriate to switch the seat belt signs off. Weather is always taken into consideration along with things such as “deck angle” - in other words, if the aircraft is about to commence a rapid climb or is already climbing at a considerable angle for whatever reason, that might not be the appropriate time to release pax.