I’ve got all of TOS, Voyager, and DS9 (as well as all the movies – well, official movies, at least) on DVD.
I went to the trouble of copying all of Voyager to a big ol’ hard drive because I re-watch it every now and then and that would make it easier. I kindof intended to do so with DS9 as well.
Just for personal use. Not with the intention of sharing it or selling the original DVDs or anything. Not that that 100% for sure makes the act of copying “legal”. I’m unaware of any caselaw indicating it is, though maybe the “Betamax Case”'s declaration that timeshifting is legal might push the likelihood slightly in the direction that maybe courts would find it legal if they haven’t made any decision directly about copying just for personal use and not publishing. (IANAL, not legal advice, go hire a lawyer.)
But one disk was encoded differently than the rest and somehow I wasn’t able to get all the content onto the drive in a form that I could reasonably watch it from the hard drive. Even though it works just fine in my Bluray player.
Maybe one day I’ll figure out how to do put all the content on a drive, but it’s probably just as fine to swap disks as I’m watching.