I think Peirce is still working on this strip because since Peanuts and Charles Schultz heavily inspired him, he wants to make Big Nate go for as long as Schultz did with Peanuts, which was fifty years straight.
It wasn’t even a good idea for Schultz to make it go on for that long since even his strip had a drop in quality in its later years.
Twist: Miranda is Chester’s little sister