I have to agree, sometimes I split a colony prematurely, everything slow down, including eating, movement, countship... etc. For most species I have, the perfect quantity for a box is when I open the box to disturb them, there is just enough space for them to packed together and hide at the bottom layers, leaving the top 2 layers of egg crates largely empty.
For many species I have acquired, they only started become really active and breeding crazy when they reach certain density.