I lived in eastern Indiana in the U.S. some thirty years ago, and my friends in high school used "Thanks much" a lot (without 'very'). I mean a lot. However, one day I realized it was a rarity, and to date I tried not to use it even in casual conversation. But just the other day I heard people using it. Should I not use it at all, even in colloquial situations? To tell you the truth, it pops out of my mouth automatically, especially when chatting with my friends, my close friends.