In response to the OP's question, I think the pre-made industry (non-DIY) is generally on the up and up. BUT I had the same questions as you and I think the honest answer is: The only way to control what goes in to your juice is to DIY, which I do. I have VERY few vendor juices on my vape list now. Almost everything I mix tastes better to me just because you tweak recipes to your individual tastes instead of catering to the masses. There are some excellent juices out there by vendors and most vendors take extreme care when mixing in general. The thing is if your worried about the mixing issue, I hate to spring up the issue of where is the PG/VG/NIC SOURCED?? A LOT of these vendors are using products sourced in China, which for some is not a big deal, but how many vendors will tell you there bases are sourced in America. Remember, made in America does NOT by any means mean SOURCED in America, they could be mixing with chinese made bases/flavors in America hence "made in America" Again, a lot of people don't mind this, I'm just saying that I do. YMMV