The device is going to play a huge role in how long you puff on it, if you are vaping on something with a tight airflow and doing mouth-to-lung inhales then you'll probably be pulling on the device a bit longer than if you are using something with wide open airflow and a lot of power.
I do straight lung inhales on most of my attys and can fill my lungs in about 3-4 seconds, I rarely use my kayfuns anymore but when I do I go with a mouth-to-lung inhale which usually lasts around 6-7 second, although even with a 6-7 second long drag I still only get a tiny fraction of the vapor that I get from more open tanks in 3-4 seconds.
If you are getting a satisfying vape on a given device that's all that matters
