I've probably not gone more than a week without dumping.
But, I also do not clean my black tank or hose it out or any of the other heroic efforts I sometimes read about here. I always put an enzyme "poop packet" in the tank before a trip, and when I get ready to dump I have a small piece of wood that keeps the toilet valve blocked open so that I can top off the black tank with fresh water. Once it is full, I dump.
My RV is 28 years old, and I have owned it for about 10. The sensors operate great. In the day time you can see down the hole to the tank itself and while not "clean", you can see daylight through the holding tank walls.
I don't think there is any need to hose down or otherwise clean the black tank.