AppleCare+, since 2019, has been renewable (presumably until Apple declares the product obsolete) for most products except the AirPods (in my experience) in the following countries [1]:
Australia, Austria, Canada, Denmark, Finland, France, Germany, Ireland, Italy, Japan, the Netherlands, New Zealand, Norway, Spain, Sweden, Switzerland, the United Kingdom and the United States
AppleCare now has monthly until you cancel plans - not just for watch but for phone and even the monitor. (I'm not sure of the macs). It's a bit confusing when you order and I'm not sure if it's because Apple is trying to discourage this; I just decline during order and then add it separately and this option always shows up for me.
You can buy AppleCare+ monthly indefinitely (until they EOL the device) at a monthly rate. You can even renew it after the 2 year length into a monthly plan.