There isn't a "LANDesk detected a reboot is needed" type switch -- all that happens is much simpler really .
We check the "PendingFileRename" registry key (that's a normal Windows thing), as it's a very easy way to check whether a reboot is required - the OS handles that.
Now, it's surprisingly common that you may need 3-4 reboots to actually clear that stuff out (installs "completing" themselves only after a few reboots, and so on) -- though I'd advise against "just clearing" that registry key out, as this is relevant information for the OS to actually go and replace files that are currently in use with newer ones.
This should help you with your issue though, I hope - so you can check on the clients locally what's going on.
Depending on the files that don't clear out / keep needing you to reboot your clients, you may even find a misbehaving app or so, which may help you with your environment.
Hope this helps.
- Paul Hoffmann