Our heat and light goes off at night, as the temp can drop to about 18 degrees centigrade and the beardies are happy with this. So it depends what temp the room you have them in drops to. We have a heatmat in place for winter just to add a little extra heat if needed (its on its own thermostat). In the wild obviously they have a large drop at night so this seems to be best for them in captivity too.
Another thing I forgot to mention - have you got calcium supplements and nutrabol to dust the crickets? We do weekday feeds in the morning with calcium and weekend feeds with nutrabol in the morning!