I'm not sure if this has been covered very well. I'm aware of several complaints of pre-heat rush with the 40. I've experienced this problem recently and it isn't a problem with my chip. I do agree that this is an aweful experience. Beforehand I couldn't figure out what all of these people were...
I wrote this for a couple of friends that are interested. Sharing it with you and hope it helps.
Liquid calculators:
Do It Yourself E-Liquid (E-Juice) Recipe Mixing Station!
This is the what I use the most:
DIY E-Liquid Calculator With Ten Flavors
Your mix will consist of these four basic...