There seems to be some misunderstanding in these comments in how Google Analytics works:
"The Average Time on Page trend line should give you the information you need without resorting to this."
Incorrect, if no further events or pages are clicked, time on site is ALSO incorrect.
"You'd have to research to make sure that your hack isn't also artificially inflating the number of pageviews, increasing the pages / visit and artificially deflating the Avg Visit Duration."
This hack is tracking via events, not pageviews. The last item would be the opposite, it would increase the average time on site, not decrease it. However, that is another Analytics issue.
"Firing on timeout is not the ideal way as the general pattern tells us people open multiple tabs which they may or may not read."
This IS true and a valid way of measuring. Though some might still prefer a time based approach.
As a person who's done GA implementations and subsequent reporting on around 100 websites this is correct.
On a side note, a tangential GA issue was recently discussed on HN and nearly everyone had a misunderstanding of how GA worked in that thread too... sometimes I'm worried that developers will get wise to analytics and I'll be out of a job, and then I come here and my fears allayed.
The thing is, GA is very simple and it all works together. I'll leave the below link here, because I think a lot of people could get value from it...
Regarding the multiple tab issue, you can use the Page Visibility API [1] to determine if the page is still visible before firing the timeout event. It's a pretty handy API for other things, too.
"The Average Time on Page trend line should give you the information you need without resorting to this." Incorrect, if no further events or pages are clicked, time on site is ALSO incorrect.
"You'd have to research to make sure that your hack isn't also artificially inflating the number of pageviews, increasing the pages / visit and artificially deflating the Avg Visit Duration." This hack is tracking via events, not pageviews. The last item would be the opposite, it would increase the average time on site, not decrease it. However, that is another Analytics issue.
"Firing on timeout is not the ideal way as the general pattern tells us people open multiple tabs which they may or may not read." This IS true and a valid way of measuring. Though some might still prefer a time based approach.
This repo https://github.com/rockymadden/gap explains most of it.
Lastly, see Google's own word on this (tl;dr it's perfectly valid): http://analytics.blogspot.com/2012/07/tracking-adjusted-boun...