I suspected that you might want more.
What that script shows you is the last time that the user(s) logged on and the total number of times they have logged on.
What it doesn't show is when a user logged off and the total number of hours that they were logged on.
For some of that info, the EventViewer can be useful, however, as you have seen, the clearing of the logs will eliminate past event log entries.
True is that with group policy you can restrict the use of EventViewer.
I suspect that your users don't have the slightest idea what event viewer is.
Although supposedly there is a "LogoffTime" property, the info doesn't seem to be there. Whether this is operator malfucntion or a "feature" of the netlogons is beyond my knowledge.
I seriously recommend visiting a couple of powershell and/or admin forums to see if someone there will, for no renumeration, write a script for you.
http://powershell.com
http://powershellcommunity.org
http://blogs.technet.com/heyscriptingguy
There are many more, I just don't have a convenient set of bookmarks for PowerShell-mostly just RSS feeds