Hours Policy

Theoretically, the answer is yes.

Windows allows to REPLACE the standard logon programme with a custom logon application, and I have supported an application working this way.

Windows itself has no feature suitable for your need, as you found.

The problem is that you will need either to found an existing logon application suitable for your need (I have no idea where, the few I know of are all proprietary an not suitable for your need), or write one yourself from scratch. I can point you to a company who has made their own one, but I doubt that they will be cooperative.

The only thing that pops into my head right away would be a VBscript tied into the suers logon. The tricky part would be how to control things. You could for example write the script that looks at the intial time and then increments itself a set amount of time (i.e. 8 hours) and then once it hits 8 hours would kick off the shutdown.exe process. This is not very gracefull but should do what you want. Of course the easy way for a user around this would be to change the time on the computer they are on, however you could lock them out from doing this via group policy or have the script look to a server for the time where the user in question has no access.