As with any lossy encoding process, I also always keep my originals so I can do it over in the future if need be :)
Not necessarily the physical disc but at least an ISO. I tend to rip DVD ISOs with the encryption intact in the name of making an untouched copy, since CSS is so thoroughly broken and since I have seen some very bad “backup” tooling that corrupts the VOBs when decrypting. I use DVDfab Passkey which is free for DVD usage; “Rip to Image” → “Keep Protection”.
Not necessarily the physical disc but at least an ISO. I tend to rip DVD ISOs with the encryption intact in the name of making an untouched copy, since CSS is so thoroughly broken and since I have seen some very bad “backup” tooling that corrupts the VOBs when decrypting. I use DVDfab Passkey which is free for DVD usage; “Rip to Image” → “Keep Protection”.