Persistent render results

It would be a great help if the render results (1-8) could be made persistent over Blender sessions. Looking at the renders of the last time you worked in this file and the render times / noise levels greatly helps continuing my work. I don't want to bloat up every Blender file save with additional multi layer renders by default, but at least please make it optional to save your render results if the user wishes so. Or use a persistent temporal folder for them and give us an option to reload them all with one click.