Thank you for your reply Loner T. I have checked the Advanced Settings. This is where I wasn't able to select "Sleep" for a few settings. I also wasn't able to put the laptop to sleep manually.
What I have discovered is that Firefox and other application cause an issue if left running when closing the lid. Firefox in particular will display "not responding" which ends up heating up the laptop. It seems like Firefox hangs due to the network link being dropped. However, this doesn't explain not having the option for sleep at all. After a restart, the options came back. I know a simple restart isn't the fix because we have restarted many times before and the issue persist. The common setup among the computers having the issue is external displays. The displays are all connected via a Thunderbolt to VGA adapter or direct to an Apple display via Display-port/Thunderbolt. It seems like Thunderbolt is causing the issue. Windows won't recognize Thunderbolt devices connected after the Mac is already booted. Thunderbolt devices require a reboot in Windows but not OS X. This hardware issue must coincide with the "Sleep" issue. I was able to replicate the issue and determine that the "Sleep" option is gone while a Thunderbolt device is connected. If the Thunderbolt device is disconnected and a reboot is performed, the "Sleep" option returns.
I will do more research online now that we have isolated the issue. I wonder if it is a limitation of Windows 7 & 8. Hopefully it is resolved or improved in Windows 10.
