...& getting your 5 stacks back when returning to a game you were disconnected from.
This does not happen. Yesterday I got disconnected and had to log back in to Diablo 3. I immediately clicked 'Resume' to play again and all my NV stacks were gone. I was out for probably 2 minutes at most. The stacks need to remain on your character for the full 30 minute duration, so if you kill an elite pack and get disconnected, and you can only log back in 25 minutes later, the NV stack should still be there.
I think that only happens in a party. My brother disconnected and rejoined, had 5 stacks still.