What r.sander says
We have 21500 devices which are classified by a big bunch of custom tags.
This is location, country, type of device, switchport count, manufacturer, type of application/webserver/database, type of OS (Windows, Linux…) etcetc…
And only with those tags we enable/disable checks and services and peridic service discovery. No rules in folders and subfolders.
Activation takes a long time now but the rules.mk is portable to other instances