As will all WMI properties, please set these to evaluate less frequently than ‘Every Report’. WMI is a great way to pull information, but it has inherent performance penalties…
Note that we already provide this property in the Analysis “Hardware Information (Windows)” on the “BES Inventory and License” site. The relevance we use to retrieve the screen resolution is slightly more advanced than what is posted here and I encourage you to use this Analysis (the “Hardware Information (Windows)” is commonly considered one of the most useful Analyses that BigFix offers).