Why does Discovery Data Manager spend so much time rebuilding .NCF files for other Primary Sites and their Child Sites when ConfigMgr 2012 starts?

Why does Discovery Data Manager spend so much time rebuilding .NCF files for other Primary Sites and their Child Sites when ConfigMgr 2012 starts?

I’m running ConfigMgr 2012 Hierarchy.

What I’ve noticed is that on my Primary Site Servers Discovery Data Manager (DDM), is spending a lot of time rebuilding Network Configuration Files (.NCF) for other Primary Sites and their Child Sites when ConfigMgr starts despite my Boundaries not changing since the last time the .NCF files were rebuilt. As a result DDM is getting backlogged.