MacOS – MacBook Air slow shutdown time

I have a late-2010 MacBook Air and I've been experiencing pretty slow shutdown times recently. I know that there's always the "how often do you shutdown your computer?" argument but I see that as invalid because throughout the life of this laptop it has thus far had a roughly 3-5 second shutdown time. My concern is that the slow shutdown time is an early warning sign that the SSD is beginning to fail, or that there is some other component that is beginning to fail.

As an experiment I created a new user and performed a shutdown with that account and the slow shutdown issue persisted.

I also have FileVault enabled, but I disabled it and the shutdown time was the same.

For comparison, the boot time has remained roughly the same since I bought it. Fresh from the box it had an 18 second off-to-browsing time, and now that time is about 24 seconds counting the time it takes for me to enter the password and fire up Safari.

I was thinking it could be an application that is causing the issue, but I have no idea how to diagnose that other than uninstalling everything one app at a time to see.

If it's important, here is a list of installed apps, just in case anyone knows of an issue caused by any of these:

Wunderkit
Office for Mac
iWork (Pages, Numbers, Keynote)
Xcode
Photoshop, InDesign, Dreamweaver, Illustrator, AfterEffects, Contribute – All CS5
Wunderlist
MySQL Workbench
Symantec EndPoint Protection (completely disabled and not running, just installed because it has to be for work)
Firefox, Opera, and Chrome
NVAlt
Filezilla

That's all the non-apple software that's installed.

Is it possible to somehow inspect the shutdown process, like booting in verbose mode as is suggested here: MacBook Air has suddenly become very slow at booting and shutdown

Any help is appreciated

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Edit – March 13, 2012

I finally had time to try a reboot and this time it took a long time again (sometimes it is slow and sometimes it's nearly instant, which is what is making this hard to track down).

Anyway, I grabbed the following from my system.log between the shutdown and BOOT_TIME:

Mar 13 23:37:23 MyLaptop [0x0-0x1f91f9].com.apple.iTunes[2323]: Parent: Error or timeout on select
Mar 13 23:37:23 MyLaptop [0x0-0x1f91f9].com.apple.iTunes[2323]: Child with pid 2548 exited normally
Mar 13 23:37:23: --- last message repeated 1 time ---
Mar 13 23:37:23 MyLaptop [0x0-0x1f91f9].com.apple.iTunes[2323]: ATHostConnectionDestroy 0x7fe5f53e3010
Mar 13 23:37:25 MyLaptop com.apple.launchd.peruser.501[139] ([0x0-0x125125].com.apple.iCal[1410]): Exited: Killed: 9
Mar 13 23:37:25 MyLaptop mds[65]: (Error) Server: ==== XPC handleXPCMessage XPC_ERROR_CONNECTION_INVALID
Mar 13 23:37:25 MyLaptop com.apple.launchd.peruser.501[139] ([0x0-0xe00e].com.apple.iTunesHelper[187]): Exited: Killed: 9
Mar 13 23:37:25 MyLaptop com.apple.launchd.peruser.501[139] ([0x0-0x22022].com.apple.AppleSpell[260]): Exited: Killed: 9
Mar 13 23:37:25 MyLaptop com.apple.launchd.peruser.501[139] (com.apple.quicklook[2414]): Exited: Killed: 9
Mar 13 23:37:25 MyLaptop com.apple.launchd.peruser.501[139] ([0x0-0x236236].com.apple.ImageCaptureExtension2[2549]): Exited: Killed: 9
Mar 13 23:37:25 MyLaptop com.apple.launchd.peruser.501[139] (com.apple.mdworker.pool.0[1777]): Exited: Terminated: 15
Mar 13 23:37:25 MyLaptop loginwindow[67]: DEAD_PROCESS: 67 console
Mar 13 23:37:25 MyLaptop loginwindow[67]: LWCASProcessNotificationManager UNEXPECTED NOTIFICATION of type: kLSNotifyLaunchFinished
Mar 13 23:37:25 MyLaptop airportd[2596]: _doAutoJoin: Already associated to “network_wifi”. Bailing on auto-join.
Mar 13 23:37:25 MyLaptop com.apple.kextd[10]: Error reconsidering volume /private/var/folders/07/n5qt65lx44j5y4s7zg2_nv3w0000gn/T/NVProtectedEditingSpace.
Mar 13 23:37:25 MyLaptop shutdown[2599]: halt by Zac: 
Mar 13 23:37:25 MyLaptop shutdown[2599]: SHUTDOWN_TIME: 1331696245 696702
Mar 13 23:37:25 MyLaptop UserEventAgent[11]: CaptiveNetworkSupport:UserAgentDied:139 User Agent @port=29463 Died
Mar 13 23:37:25 MyLaptop imagent[166]: Quit - notifying about shutdown

Is the "error reconsidering volume" part of the trouble?