yes you are right. It's important to change. I do have the Gym Style Serie and few other weights DVD's. I might use premixes sometimes for full body workout or cardio only. May be later, I will do some circuit premixes... but I would rather do like BM2, Low Impact Circuit or Drill Max...
I feel with 4 days split and GS, I have a good variety. May be in the future when I know them well, I will look more into the premixes. God... I love the 4 day split!