It depends on who's giving the seminar and if they care to improve your skills. If they see a flaw they tend to give advice which could elevate your game tremendously, however some just want to show up quick and go home. It's a toss up, but if you follow certain fighter boards and ask fans they will tell you the guys that are passionate about the sport.
People want to be led to the truth, only you can find the truth for yourself. Then it will be with you forever unalterable and infinitely expandable.