This is one of the items that is tested in your Windows 8 App when you use the WACK.
If you are in Southern California, please email these posts for more information on getting a token for your app by June 30, 2012!
Suspends and resumes in allotted times
An application has five seconds to save state after the suspending event fires.
The application should resume just as efficiently.
Optimizing your app's lifecycle