I don't save psd files but do save my working pspimage files (same type of file only it is the native format for Paint Shop Pro software). And, my software does not save tiff files as layered files so they are useless to me. I did a test once a long time ago and the same layout created and saved as a PSD from PSE 14? compared to a created layout and saved pspimage file found that my pspimage file was 1/4th the size of the psd file. Cemented my decision to stay with PSP
When organizing my files 9 months ago I did find that I have lost a few of them probably when on an EHD that I hadn't used for awhile and wouldn't work on any computer when I did try to use it. But I have the jpgs so all good there.
Also this past year I did pull up one of my pspimage files to do a new layout. Old layout was of a cousin's son in his Navy uniform. I had the same type of photos for his cousin but had never done the layout. I wanted the layouts to look the same and I no longer have the kit I used. So old layout, replace photos and I'm good to go. Old layout was from maybe 10-12 years ago?