Welcome rjw to irv2 and the Newmar forum.
You will get alot of pro's and con's on this one but on all three Newmars I have had the slides have been locked.
One reason is I had a Bounder without a slide and I was pulling a popup when we got cut off by a four wheeler that bumped the passenger front bumper and cause the MH to swerve to the left from just a slite touch of the 4 wheelers rear bumper. The effort to bring the coach under control with popup swinging around in back, if I had slides unlocked the accident would have been alot worse with family on board and when the car was spinning around to come back and hit me again dead center at front passenger wheel.
While this was going on truckers were trying to avoid us also.
So all slides are locked, they are manual, new MH's have auto electic locks so Newmar still seems to think they are needed.
Another reason its a good idea it will keep the slide wall sealed to the gasket so no water or wind noise will make your ride unpleasent.
Enjoy the forum and do post often.