The first juice I bought was 6mg/ml. It was not enough for me then, so I bought higher-nic juices. That was December last year.
Now I use juices with varying nic strengths--from 3mg to 18 (I DIY them mostly), but only use the strong ones a couple of times a day. The stuff you use greatly factor in on how strong the nic hits you--on some of my builds, I can only tolerate low nic juice (6mg and below), while others compel me to drip the 10-18mg juice so I can be satisfied.
Now I use juices with varying nic strengths--from 3mg to 18 (I DIY them mostly), but only use the strong ones a couple of times a day. The stuff you use greatly factor in on how strong the nic hits you--on some of my builds, I can only tolerate low nic juice (6mg and below), while others compel me to drip the 10-18mg juice so I can be satisfied.