I agree completely with the first part, but will disagree a bit on the deleting of interfaces. I have 10's of thousands of interfaces that are not monitored and the they generate no false alerts nor stale data as they are, as I stated, not monitored. Additionally, if at a later date I want to monitor one of those interfaces, all that needs to be done is to simply recheck the box to monitor it.
I would be interested to hear what experiences/issues that you have had that caused you to choose to delete an interface. I might be going about things incorrectly myself.