I am examining the mobileSMS.plist file from an iPad. The message retention setting was changed from "forever" to "30 days" as documented in the file. I am trying to determine the date/time the change was made. One suggestion was that the "SuspendTime" value is the time the retention was changed however when I test it with another iPad, that value does not seem to change. I have searched online for a breakdown of the values in mobileSMS.plist but have not found anything.
Does anyone know how I can determine A. the date/time the retention setting was changed and B. if there are any other variables besides human interaction that could change the retention setting. Thanks in advance.  

Apple has made some changed to what is stored on the device in order to save space on devices and also charge for additional iCloud storage. A couple of months back there was a change in SMS storage. Have a look online.