I've really enjoyed reading all of the responses. So interesting to hear the different perspectives.
For now, I'm keeping all versions of more recent layouts. Maybe several months back? Beyond that, I deleted the layout PSD file and the web version. Kept the original 12x12 size jpegs and the size I print at...8x8 jpegs. (I print at home and do it mostly right after I make the layout unless I run out of paper. Drats! lol That happened a few weeks ago and I wound up having to print about 20 at one time after I got the paper.)
Except for any layouts that I did something a little more "special" on. Like made myself a template for a shape or some layers or something. So, there's a handful of layout PSDs that I did keep.
And I DID switch to TIFF files for the layered files. If I open a PSD template, I save it right away as a TIFF and get rid of the PSD version. I'm saving my layered layouts, now, as TIFF. What a space saver! And I LOVE the previews!
Oh, and they supposedly were able to retrieve 186,670 files off of my busted EHD. I'm guessing more than half of that I don't really care about.
Thanks for all of the help, suggestions, knowledge shared and opinions.