I can't say it is a strategy, but generic images I set as RF. Places and special locations, I set as RM. Some animal or plant images I may set as RM too.
However, in sites that only have RF (such as Shutterpoint), I may have the same images I have as RM elsewhere, but if I sell it in one place as RM, I disable the images that are RF (and reupload them as RM where possible). Would also do that in the oppposite direction, but this hasn't happened yet. In fact there are two images in SP I keep there, although sold as RM elsewhere, but I set them at US$9,999 so I doubt there is any risk anyone will buy them.

Of course I only do what I said above in places I have the possibility of deleting an image at any time, and these are not the images I have at the micros (I have two separate portfolios).
Regards,
Adelaide