how do you calculate the session duration? is it the delta between two page hits or similar events? i tried a couple of the smaller analytics tools, like plau

how do you calculate the session duration? is it the delta between two page hits or similar events? i tried a couple of the smaller analytics tools, like plausible, simpleanalytics, umami etc... and one thing that i always disliked was the way the session duration was calculated - i have a lot of longer articles where the visitor stays for a long time and then leaves. most of these tools will count that as a bounce, as there is no two hits to calculate the delta between. but for me it is a very important metric to get accurate numbers on, which is impossible with that implementation for sites like mine (very few but long page visits, not a lot of navigation between pages). do you handle this the same way? that would be a feature i'd be willing to switch my current tool out for.