Following up a post on Wed, 19 Nov 2014, from mark lewis to Todd Yatzook:

 ml> in your General Settings, you probably have an Inactivity timeout
 ml> of 300 (5 minutes)... can you test if you change your inactivity
 ml> timeout to the same value as the login time and see if you get the
 ml> warning? try 3 minutes for both and then try 10 minutes for both...
 ml> you already know what happens with 5 minutes ;)

it should be obvious that the inactivity timeout setting is in seconds so
for 3 minutes it's 180 and for 10 minutes 600 ;)

)\/(ark