I'm using urban
Displaying too much information sometimes not quite healthy. When we display exact time when the user last online time it might backfire on site(specially start up site) with lot of users' who hasn't logged in for a while. When new users see most users hasn't logged in for a while, its discourage them to contact users hasn't logged in recently. At the same time when user who hasn't logged in for a while not getting any messages they just forget about the site and fade away.
Instead of displaying the exact time it might be better give just a general idea when was user last seen.
Online - no change, when user online
Away? - user offline witihin an hour
Last seen few hours ago - when user online less than 6 hours ago or so
Last seen within a day - when user was online less than 25 - 30 hours ago
Last seen within 3 days - when user was online less than 75 hours ago
Last seen within a week - when user was online lass than 175 hours ago
Last seen within a month - when user was online 30 days or less
Last seen more than a month ago - when user was online more than 30 days ago
**? May be as a premium feature paid members can see exact time user was last seen
**? Also paid members can see when was the user joined the site