It's not way cheaper long-term at all, I mean unless you really watch/listen to a tiny amount of content, you can rip the same way with Netflix, Hulu and so-on as well so I don't see how that makes it more durable?
What you are doing is practically the same equivalent as downloading torrents, how do you have "more guarantees" than just downloading?
PS: I'm saying this because what you are doing is already illegal so there is virtually no difference.
If you buy the DVD and rip it to make it easier to watch / as a backup, it might be legal in your jurisdiction.
It's definitely cheaper long term for me. I don't watch/listen to a tiny amount of content, but the cost of buying the stuff once and never paying a dime after comes out far ahead of the cost of a subscription every month for life.
That depends on your jurisdiction. In mine it is legal to rip DVDs or BDs I own to watch later and for backup.
I own many of my favourites in this way.