There are two ranges that contribute to the reluctance of particles to collapse within a very short distance: the Compton radius works at larger ranges.
At a much shorter range is the quantization length, which is the length of a wave cycle, and limits how many opportunities there are for collapse within the wave cycle, because the quantization condition only exists once per cycle per wave.
When a wave is collapsed, there are lower limits on when the waves in that boson may next collapse, which is somewhere around 1/4-cycle. We predict that particles at the very highest densities may only collapse at (n + 1/4)-cycle, ± its mass-energy. So the first opportunity is at 0.25, the next at 1.25, and so on. If one of the boson's waves is collapsed, then another sequence of lengths is interleaved with the first, with the new solutions being exactly every n-cycles.
We are investigating whether this is an origin for the 'mass gap'.
Having said that, there is almost no upper limit on the number of different waves that may collapse within a volume. The real limit here is how many bosons may overlap and then trigger within a tiny space. The bosons with very little mass-energy, and slightly different phase values, will successfully overlap. Phase-coherent bosons with high energy are most likely to collapse. Therefore, the most likely plasma to collapse within a tiny volume, to create the densest concentration of fermion instances per unit volume, per unit time, are pairs of bosons from different sources, tuned to the same phase, but at a different phase from all the other bosons in the plasma. This is beyond experinemtal means, and is difficult to achieve in even extreme natural conditions, but it is statistically possible to achieve this contrived example.