I'm not an expert on AD, but from what I've seen, unless you're using roaming profiles, the amount of time someone spends connected to the AD server is just long enough to do the authentication song and dance. And that's only the first time a particular user logs in on a specific machine. After that, Windows caches the login info.
So, without roaming profile use, such information would seem rather useless.
Is there any way to knowk which users are conected to the active directory at any time, any command like net users or net accounts for example