I think its hard to say with the different concentrations of different vendors.
Anywhere between 2-20%, depending on the flavor(s).
I try to stick below a total of %15 so normally for 1 flavor of a two flavor mix is usually %5ish
I think my lowest is 12 and if I go over 20 I normal work it down to 20 slowly
Depends on the flavor. I rarely exceed 15% on a single flavor, and try to keep the total flavor % below 25%
15 to 30%
20-30%, I like strong flavour.
15%