Apple Watch Ultra 1 vs. Ultra 4 Buyer's Guide: Is It Worth Upgrading?

The Apple Watch Ultra 4 arrives four years after the original model. Across three subsequent generations, Apple added a brighter and larger display, satellite connectivity, new health sensors, more capable chips, and longer battery life. For owners of the original Ultra, are those cumulative improvements enough to justify upgrading now, or can their existing watch last another year?