Average Duration is a very important metric to understand about your sites performance metrics. there are lots of ways you can use average duration gain sites into your online visitors. You can measure visitor engagement between two separate time periods and correlate that to your online marketing activity as an example.

So because a few people complained, bloggers mostly, and were too weak minded and lazy to make the appropriate changes in their spreadsheets Google Analytics has produced an inaccurate number for “site duration” ever since.