One big pain point we have with scheduled discovery is that an automated subnet scan will refind all of the disks, network interfaces etc that we have already disabled - then renable the D*&^#$ed things.
Please allow scheduled discoveries to IGNORE EXISTING HOSTS 
In its current form we have banned the use of subnet discoveries - its causes days of work to go back and re-disable all the disks and interface again.
This was a request a few years ago but got nowhere.
Feature Request - Delete Node and/or Interface with Discovery Ignore Option