This is a bit difficult using the standard product. You could look at a combination of items such as the Last Started date/time in the software inventory. If you pick a major app then that would indicate if it was getting launched. You could combine this with the Last Boot date/time in the OS section to see if machines are getting restrated. Nothing solid though I suppose as the data is snapshot data and machine focussed.
If these don't help then perhaps consider our State Notifier module. This is real-time updating of systems and monitors the state of the device as well as the user state so that you can map out utilisation. For example, if a machine spends most of it's time offline or with the screensaver running then it indicates an under-utilised system. Might be worth a look.
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