Subscription
If I have a yearly subscription to Apple TV. Can I watch it offline for longer than 30 days. I am attached to a ship and don’t have WiFi access aboard
The documentation says 30 days for most Apple TV app Channels, and some may be less.
Download and stream shows and movies from Apple TV+ and Apple TV channels - Apple Support
Unfortunately for you, this service is not aimed at users who are offline for that long.