Dumping half bath black tank every other trip or so?

I fully rinse the black tank, use my santi flush, then add a cup of Calgon water softener and cap of Purx laundry crystals then at least four to five gallons of water. Don't believe in a dry tank ever, but I live in "no winterizing area"! Two weeks ago my wife and I were in our backyard. She smelled lavender. The Montana was parked on our street below grade. It was the tank we smelled. I said imagine what the smell would be like if we did not take the time to keep tank fresh! :)