If you are going camping once a month during the season or more frequently (hopefully
), just leave the water in it. Won't hurt anything and you won't have to fill the tank before you go just to make sure it is still water tight.
Wear on your anode rod, whether in water or not (there is humidity in the air inside the tank) is normal; that's what it is supposed to do. Pitting and cratering is nothing to be concerned about, just normal "sacrificing" instead of the same thing happening to the surface of your tank, and trying to keep an anode "pristine" is an exercise in futility...just let it do its job. Unless it is wrapped in plastic (that's how they are shipped from the manufacturer of the rod), it will corrode just sitting on a shelf. Most people also tend to replace an anode well before it is necessary, based on "how bad it looks". It, as opposed to the inside of your tank is supposed to look that way. You shouldn't have to replace an anode until you can see the rod it is built around (yep, there is actually a steel rod inside the zinc) and you will normally see it first at the junction of the rod and the nut. Just because it is pitted and lumpy (kind of like me), you don't need to replace it (nor am I in need of replacing, despite my looks!
Always store it "installed" into your tank...it won't do the tank any good if it is sitting in the garage or storage bay. Put it in the tank (keeps critters out also), let it corrode (that means it is corroding and not your tank) and let it get really rotten looking (you should see the rod) before replacing. The anode rod in my old '08 210WBS was never replaced, spent well over a year and a half's worth of days in it, all across the country, in every type of water imaginable, and it is still going strong for the fellow that bought it when I got the 5ver.