I recall taking this route a few times in the past, but not recently. I know some state you shouldn't take overnight buses, however in a place like Bolivia that can be rather difficult to avoid. Some routes that is the schedule or it becomes necessary to cover the distance. What I've seen before that is common on some routes, is the bus leaves the station and the bus driver will stop to pick up additional passengers even when there aren't any seats. I doubt the company knows about this. Usually these folks are relegated to sitting/standing in the aisle and so I'd strongly suggest you always keep your daypack and valuables close to you and not in any over head storage, just too many people around.