[Lazy_Perfectionist]

If I've got conveniently placed independent scout recruiting points, I churn out scouts nearly nonstop until I've saturated nearby nations. I even find it helpful to place scouts in the lands of trustworthy allies. If they're facing a deep, hostile invasion, it will let me know precisely what I'll be facing if I launch a relief effort, or aim assisting assassinations.
Or, if the invading force moves on without leaving any province defense or troops behind (it happens), I get to mess with their lines of retreat.