[prndl]

Lot's of comments about stress on the frame. Where do you get stress on the frame? The slides are not structural components of the frame. The trailer frame does not care if the slides are in, out, or missing.
Now driving with the slides out or maneuvering in a space with them out could be a hazard but probably only to damaging the slide hitting something or someone or blocking the view rearward. Could also cause the slide to be offset in orientation.