To the OP
No. Never leave it for that long. As mentioned, it will dry out, become a hard mess and you'll have a dickens of a time trying to get that stuff out.
I like to dump after every trip, but sometimes, after a weekend and there is no good place to dump, and I know I'm going out the following weekend I will let it "stew" for a week.
At the end of the season, when I know we are not going out anymore, I will pay at the campground near us to dump. There, I can use their non potable water spigot to flush the black tank.
In cases where I'm not paying for a service, I will not use the black flush if anyone is in line to use the dump station.
But to repeat, don't let a half full black tank, or for that matter, any stuff in a black tank sit for as long as you are suggesting.
Except when I've winterized I will always put a couple of gallons of water in the black water tank. When I've winterized, I will put some anti-freeze in the black tank.
Erroll, Mary
2021 Coachmen Freedom Express 20SE
2014 F150 Supercab 4x4 w/ 8' box, Ecoboost & HD Pkg
Equal-i-zer Hitch