The big reason why I throw away camera originals (Canon), even with the Pentax too.. Is 1) Image data verification! (saved me several times!)
I wonder, why did your files get corrupted? And if they were detected as being corrupt, how did you repair them, without the originals still available? And do you realise that the repeated writing of the DNGs, every time the file is edited and new XMP data has to be written, increases
the risk of something going wrong ...
2) I get to rid the raws of their useless (to me) full-size jpg previews - can save ~3-6MB per file with having no previews
Useless to you, not useless to others. Even if the Raw data would get corrupted, one can often still extract the Preview. But I agree that it's nice to be able and write one's personally preferred preview size.
3) Holds xmp inside for belt-and-suspenders backup of metadata & develop settings/snapshots (although could be considered bad by some because of backup reasons)
Besides that that XMP data is only useful inside an Adobe application like LR/ACR, the required additional backups, even if the Raw data itself didn't change, but the XMP data might have been, the repeated writing of changed XMP data causes the entire file to be rewritten to disk. Besides causing potential disk fragmentation (and wear on SSDs), each write holds an inherent possibility of data corruption. Since the verification data is held inside the file, there is no way of verifying with absolute certainty that the file as such (including verification data) was written correctly. The verification data is calculated from the Raw data which was perhaps changed by memory module error during editing. Only when reading the file next time, is the verification data compared (assuming the file as such was readable), and since it was calculated from potentially corrupted data, it will report that everything is fine. Even rewriting the verification data itself seperately over and over again is bad for security. Once calculated and verified, one should not keep recalculating and writing it, it only adds to the risk of something going wrong. Maybe that's what you've experienced?
4) Can use lossless DNG for those shots that you just can't quite seem to throw away.
You mean that you normally write 'lossy' compressed DNGs? Or do you mean that it is possible to encapsulate the original Raw inside a DNG wrapper? The latter seems a bit of a convoluted cludge, why not just keep the camera original? It will get converted on the fly anyway when it's read by LR/ACR.
Camera original Raws have other benefits, such as for some Canon files they can hold dust removal data, and they can be lens corrected with the DPP application very well, and the colors are often reported as superior. With the advent of sensor shift technologies to improve the Bayer CFA color accuracy per pixel, and resolution enhancing half pixel shifts, it gets increasingly difficult to store such solutions in a DNG wrapper. We've seen it with Foveon file formats, and also for Digital camera backs that store a lot of additional (blackframe and other calibration data, and need LCC corrections), we'll see it with the Lytro kind of solutions, stereo file formats, etc.
For me, there is absolutely no reason I'd even want to save camera originals anymore.. The verification part alone is valuable beyond belief!
It seems you might need to give that some more thought. While the verification feature is not entirely without merit, it does give a false sense of confidence. But then that happens more often with (DNG) fanatics ...