Weight is a key question on the Camino. A sleeping liner seems to be a much better solution with its 200-300 g weight than a 800-900g sleeping bag.
From the middle of June until middle of September, when the outside temperature is always above 30 C travel liner is adequate. Don’t forget that there are no air-conditions in the albergues, so summer nights are too warm to sleep in a sleeping bag.
In autum, winter and spring always take a sleeping bag with you but choose the lighter version (800-900 g) which is comfortable between 10 and 20 C. All the albergues has heating, so the temperature never goes below 10 C.