The Help text for the Advanced Setting "Days to Expire History Images" needs to be updated.

To force DF to work through all images in the local Wallpaper image library, this should be set to "99999". After all images have been displayed, DF will delete all the image history for that monitor and start over. With multiple monitors (physical or splits), this is handled on a per-monitor basis.

I haven't experimented with monitor profiles because I don't use that feature very often, so I don't know the implications for wallpaper history management.