Hey Kent and Iris - welcome back to America!
As Robbie Burns wrote, "The best laid schemes o' Mice an' Men Gang aft agley"
- sounds like you're one of many with crjuising plans changed due to C-19. Hopefully you'll be able to get out there in the not-too-distant future.
Regarding your furler gearboxes, there's a thread from 2016 you can search for more discussion, but Bonfiglioli ships their's with Shell Tivela S320 and calls it "lifetime" lubrication, with a 25,000 hour life. There are many equivalent Industrial Synthetic gear oils out there that a google search will bring up.
That being said, our application with infrequent short duration use really doesn't demand the hi-tech oil. Perhaps more importantly, the harsh environment with risk of sea water intrusion past the lip seals may argue for the addition of Zerk fittings enabling frequent greasing that many of us have done. That you've had years with no water intrusion is great so you may want to choose to continue as is - no "right" answer.
Craig - if the Covid subsides we may scoot up your way - will let you know.