Not really. If the discs you have play today, they may or may not continue to work offline depending on the player, but every so often discs are released your player won't have the right keys for and those won't play until you connect your player to the internet so it can download the newest set of keys. Some keys will expire after a certain amount of time (for example the PS3 warned they'll only last 12 to 18 months https://manuals.playstation.net/document/en/ps3/current/vide...) and you'll have to connect the player to the internet to watch content that used to work. The manufacturer of your player could also shut down their server and stop providing updated keys and then you'd have to buy a new player to play any new discs. New discs can also break your old players (https://old.reddit.com/r/techsupport/comments/vcaniv/help_wi...). The capability is also there for them to revoke keys entirely which will stop your old discs from working even if you connect to the internet and you'll be forced to repurchase your movies, but I haven't seen that used so far.