This is what I do.
I add all my devices (the ones where I want to backup the config) to NCM. Then I've created a job that backs up the startup config. Then 1 hour alert I run another job that backs up the running config and as part of that job I compare the running config to the startup config (so that I can see where configs haven't been written off). I run these once a week. So once a week I get 3 emails (one for startup, one for running and one for the comparison). I look through these to see which backups didn't work and which configs haven't been written off).
And I've turned on real time config change detection so that it automatically backs up the running config when a change has been detected.
To see which nodes aren't in NCM as yet, go into Manage Nodes and select NCM - Licensed in the 'Group by:' drop down. Then click on the No group and you'll see all the nodes that currently aren't in NCM.