Kinect Sports Season Two
70 Achievements
1,500
60-80h
Xbox 360
Kinect Sports-a-thon
Played Kinect Sports: Season Two for more than 2 hours (cumulative time)
25
How to unlock the Kinect Sports-a-thon achievement in Kinect Sports Season Two - Definitive Guide
Pretty self explanatory solution here. I got this after playing a couple fun sessions with friends and family. Just enjoy the game and this should com naturally. There is no reason to try for this achievement as trying for any other achievements will most surely take you well more than 2 hours.
Obviously, this comes naturally. Just play!