There is no actual duration for the stance. Think of it more as every flurry a chunk of your pets "STA" is lost, it's not a constant drain. So you can activate it, let 3 flurries go, pull your pet back, go make a sandwich, come back and still have 6 flurries locked and loaded for the next mob the pet attacks (your pet gets 9->10 flurries per activation, not sure how it's worked out but it varies some times). Yea it's not a ton of dps it's FREE dps, doesn't effect you in any way. So ~9 extra rounds and ~9 extra proc chances is not gonna revolutionize your pet its still more than you had before. The recharge time may be a bit long but maybe it could be reduced with pet tomes (thinking along the same lines as the pet armor/resist/crit)