Another problem with this is that, if a user logs onto more than one workstation or shares his/her password, the data you collect is not going to be very accurate.
It may only be worth it if you have smartcard authentication on your workstations, and then the user has to have the card in which to log on/log off. Again, even with this,(certainly for your techical support staff) you have the problem of logging onto more than one PC, and the risk of data mis-interpretation.
If you are having smart cards, surely it would be easier to issue them with one which will allow swiping into the building. This is not as difficult or as expensive as it may initially seem.
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So often times it happens that we live our lives in chains
And we never even know we have the key
Ne auderis delere orbem rigidum meum
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