As far as I know this isn't available with what lansweeper collects by default. I've also never found lansweepers logon information to be very useful since the 'logon time' always seems to be recorded as the time lansweeper scanned the machine.
I've been able to collect this information, but it took a 3rd party app, a script, a gpo and lansweeper collecting registry keys my script wrote.
Here's what I've done. I used WinLogonView from NirSoft.net and with a GPO set it to copy the contents of that program along with a script I wrote to the local machine. This GPO then creates a schedule task to run the script at start up.
And what this script does is runs WinLogonView with the command to save it to a file, then it parses the file adding all the logon times together and puts that into a registry key. It also writes the first logon date/time and last logon date/time so that I can see how accurately calculate how much its being used. I also count how many logons there were so that I can see the average use per logon.
Once that information is written to registry lansweeper can pick it up. And now that lansweeper has it, its simply a matter of writing the report.
-Kris