First time seasonal.. question on tanks and slide?

I always left the tank as the maintance guy who put the trailer on site and hooked up the PVC for the sewer said that is how most at the campground did it. The though was since you are not towing and letting water swish around in there then that was the next best thing. Worked for us for 11 years. The awning we left out to protect the table, chairs and whatever else we had under there. We only had an awning a few years and upgraded to a hard awning.