As far as I know, if you clean up your temp file, logoff should take less than 30 sec.
Depends on your virtual memory settings, ie. the size of your pagefile and how much of it you used during the last session. A 1.5 GB pagefile that's been "exhausted" can take a while to clear depending on the processor speed.
Not that i know of. How would I check?
Go to control panel/administrative tools/local security policy/local polices/ securities options/shutdown: clear virtual memory pagefile, right click on it select properties and check "disable".
Other custom scripts to clear temporary files, prefetcher and other settings ...I'm not sure where you'd look, but like clearing the pagefile you would have actively done something to set them up. I just thought you might've done this and not made the connection to it slowing down the shutdown.