Here's a new tip from Cliff Young, AutoCAD Test Development.
Is there any way to freeze layers in vports but, not in model (layout) space?
To freeze a layer in a viewport, there is a property in both the Layer Manager and the Layer panel on the Ribbon called "VP Freeze". This will freeze the layer in the current viewport. "New VP Freeze" will freeze the layer in all subsequently created viewports. There is also a button on the Layer Manager, "New Layer VP Frozen in All ViewPorts", which creates a new layer which is frozen in all existing Viewports.