The only people that don't have that problem are those that don't use their tanks.
No problem with the grey water tank but the black tank only reads empty twice a season, before my first trip and after my last trip.
We just came back from Maine which was our last trip of the season.
Before leaving the campground on the last morning I used a wand inserted into the toilet and gave it a good flushing. I have a short clear piece I put on the dump connection and my wife watched until it ran clear.
One word of warning, don't trust that little plastic shutoff valve on the Camco wands. I use a good shutoff on the hose and attach the wand to that. (Don't ask how I learned that. )