Most of the folders I have seen are single barrel thus there is no lateral force applied to the hinge pin or barrel lump when that single barrel is fired. The double on the other hand has lateral force applied dependant on which barrel is fired.
This 'theory' may be total, whatever is the polite word for merde, but it makes some kind of sense to me.
On the other hand the majority of folding guns I have seen in the past thirty or so years did not last long enough (mechanically) to show any looseness. Going back a bit the old BSA singles etc seemed to last forever.
