Compost Bin Worm Spawns

Problem: random spawn worms/pythons ruining humus purity even if efficiency is 100%+
Example: Bin holds 7 purity pythons, so efficiency is maxed. Now comes a fresh worm/python that has no purity. What follows is: the non-purity worm/python is included into the formula that calculates the humus purity, although the efficiency is already filled by to max by other worms/pythons.
Suggestion:
-make worms stop spawning if efficiency is 100%
-only include top purity worms/pythons into formula that fit into the 100% efficiency cap
-other ideas ?
My personal problem is, that one really has a hard time gathering enough good humus to constantly plant fields to get more good stuff to get other purity up. The bins with good purity tend to spawn worms after just a few hours (or even after the first humus), so the good humus gets degraded (i had even lost a whole % after only one night and that's a big setback for newcomers). Effectively i'm not using more than half of my purity humus, because i need the top notch stuff to make progress. And this is already taking enough time without something ruining the humus purity.
Example: Bin holds 7 purity pythons, so efficiency is maxed. Now comes a fresh worm/python that has no purity. What follows is: the non-purity worm/python is included into the formula that calculates the humus purity, although the efficiency is already filled by to max by other worms/pythons.
Suggestion:
-make worms stop spawning if efficiency is 100%
-only include top purity worms/pythons into formula that fit into the 100% efficiency cap
-other ideas ?
My personal problem is, that one really has a hard time gathering enough good humus to constantly plant fields to get more good stuff to get other purity up. The bins with good purity tend to spawn worms after just a few hours (or even after the first humus), so the good humus gets degraded (i had even lost a whole % after only one night and that's a big setback for newcomers). Effectively i'm not using more than half of my purity humus, because i need the top notch stuff to make progress. And this is already taking enough time without something ruining the humus purity.