DNG Performance question

DNG 6.0.4

ok - I always like this sort of question...  (so sorry)

In terms of DNG Folder Structures and modules does anyone have any guidance on suggested numbers or what numbers cause slow performance?   We seem (as it's not clear) to have issues if we have one folder with 300 sub folders / modules under it...

I'm looking for any articles which provide help / guidance to support for DNG structure and best practice.

We prob. have a logical grouping which can be applied to breakdown the 300..

Thanks