SCCM 2012 Post Mandatory time - No more display of dialogs

Has anyone solved the problem of continuing to show the user dialogs after the SCCM mandatory time has passed? My scripts work great, asking user to close applications right up until mandatory time has passed, then no more dialogs. Should I not use mandatory time and instead set a deferral date? If I set a deferral date, how does the installation get launched if I just make it available and not mandatory?