New to TT - sewer question or lack there of

I have about 35gal tanks for each. Michigan State parks generally have electric hookups only. We only use the TT toilet for roadside emergencies and middle of the night. Otherwise, walk to the campground bathroom and use the campground showers. Like others, we tend to fill up grey first, then drain fresh. We exclusively use paper plates, plastic cups, and plasticware for eating. We only have to wash preparation dishes and pans. We have taken 3 trips of 8 nights each. First year we made it about 3 days max before takign the trailer to the dump station. Next year 5 days before slow dripping the grey and filling the fresh with a bladder tank on the roof. This year, we made it the whole trip on original fresh tank, still had to slow drip the grey.

Conservation can be learned. Or, get a portable tank.