I do it all the time... not always by choice. I get random juices from a subscription service, and for different reasons, it might be too thick, or not enough nicotine, so I keep a bottle of cheap 50VG/50PG 18mg nic and mix to to thin and/or increase nic level. I also have some lemon/strawberry I like to mix with custards for a little zing. Right now, I'm doing a little test (first "DIY") and adding flavor concentrates to a vanilla custard (Vapetasia Killer Kustard) Mix berries, lemon, apple pie, and chai tea, each one mixed with the premade custard... going to try it tomorrow. My advice (very limited experience) is it will either work great or completely mix/mute flavors and you will regret the whole idea. Do very small test batches (even just on tank at a time... shake it first to mix juices) and try some. My go to right now is the custard with some lemon. Be warned... this may backfire... or work great! Keep it simple, never mix more than two at a time.