Just a guess, but the OS could be updating the access time metadata on files/folders when you view them. Try mounting the bundle read-only to avoid this.
--EDIT Try disabling a time updates and spotlight indexing. This tutorial is intended for SSD drives but I see no reason why they would not work for you.
http://sysadmin.flakshack.com/post/9253439680/ssd-tweaks-for-mac-os-x
Disable file access time tracking Normally the Mac will keep track of the last time any file was accessed. This contributes to the wear on the SSD drive, so it is helpful to disable it. sudo touch /Library/LaunchDaemons/com.noatime.root.plist Edit the file and paste the following: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Label</key> <string>com.noatime.root</string> <key>ProgramArguments</key> <array> <string>mount</string> <string>-uwo</string> <string>noatime</string> <string>/</string> </array> <key>RunAtLoad</key> <true/> </dict> </plist> Reboot and confirm the setting with: mount | grep noatime /dev/disk0s2 on / (hfs, local, journaled, noatime) Adjust Spotlight settings Spotlight is the Mac’s indexer and search tool. While a lot of people just disable this service (sudo mdutil -a -i off), I need Spotlight because Outlook 2011 uses it for searching my Outlook data. To adjust this setting, go to System Preferences…Spotlight…Privacy. If you exclude directories that change frequently, you’ll save wear on your SSD. For example, I excluded: /Library/Caches ~/Library/Caches /Library/Application Support/Riverbed/Steelhead Mobile/datastore ~/Downloads ~/Documents/Parallels (where I store my VMs)