If you are in a multiplayer party and you quit the game and then resume you will not lose your NV stacks but all your cooldowns will reset - you can exploit it by for example make a barb with WoTB insanity, Earthquake and call of the ancients and after a battle with an elite pack , you port back to town quit the game and resume ( takes less than 10 secs ) and you get all your abilities back.
Even if you dont build yourself around it - for example just a typical WW barb you can just remind yourself that while you are in town it and WoTB is on CD there is no reason not to quit and resume. ofcourse this works for every class ( archon etc )
I know its not a huge deal but it can certainly help sometimes...