Thanks for the replies.
One of the reasons I asked is that I store all RAWs, going back to 2005, in multiple locations.
I don't store TIFFs or Jpegs for two reasons; 1. Space - it's cheaper to store a RAW than a TIFF. 2. A RAW processed on 2018 software will almost certainly be better than a RAW processed on, say, 2010 software.
There is no cost to the client for this backup service.
But, clients do screw up. Files are lost or corrupted or, quite often I find, edited and not saved as copies, so my original edit is lost.
Whatever the reason, they occasionally come looking for a file(s) and they pay for the newly created/edited TIFF/Jpeg.
Hence my question.
Thanks again.
D.