Using lots of blurred graphics in the same document can bring a computer to it's knees. Similarly, CPU intensive synths in a music sequencing application can do the same thing. In many music sequencers, there is a feature that allows you to freeze a music track by turning the synth's audio into a small WAV file and turning the synth off. Perhaps a similar feature could be introduced in Inkscape. By freezing an object (i.e. a group of blurred objects), it becomes a temporary PNG that is displayed in place of the real object. The real object exists in the document, but it is hidden from view. The temp freeze image can be moved around the canvas, but not edited at all. If you want to edit the object, simply unfreeze the object to delete the temp image and unhide the original object.
Currently, you can hide and lock objects. What is missing is a means of exporting an object as PNG, locking and hiding the original object, importing the temporary PNG at the same size and location as the original object, then syncing the location of the original object with the temporary image.
At bare minimum, a feature that would export a selected object as PNG and import the new PNG to a newly created layer (named "png copy of xyz_object") - all in one step would be a nice step in the right direction. Then, all I would need to do is hide the original object. If I want to edit the object, I can delete the PNG layer and unhide the original object.