It lasts 2 minutes. Cooldown very fast and it's ready to use before your 2 minutes are up. The great part is you can actually regen mp while this is in effect. Bad part is your fighting skills really get axed.
Silent move is great if you just want to sneak up behind a mob and backstab/lure/veil it.
Not bad, and yeah I would probably end up using it that way. What I was really looking at doing though was hitting all those fields of drops people leave behind. You know the ones they are too busy to pickup then just leave there with all the aggro mobs wandering around.