I think it’s just because of how many “units” are in a chemical thrower “magazine.” It’s currently set to 90 per unit and there’s 1000 of these in a mag. That’s…a lot.
I went into the files and changed it to 20 to see how it felt. It takes a while, but more along the lines of 20 minutes instead of 12 hours.
Seems kind of short, but it could do. Somewhere between 20 and 35 seems good to me.