Thank you for your reply.
Currently, I’m using 30m as a session cookie lifetime. As I estimate, that is the average time of user to spend on my time (from browsing through payment)
And Yes, I want to benchmark my website, like when I create a promo page, how is it perform, does the promo lead the user to other pages or they just left after open the promo page. So, I want to know how long they are on my website.
Thank you for your suggestion. I think I need to breakdown the event first like you suggested.