But as you mention, this is not an annual event... yet apparently the valve greasing IS an annual event. (go figure... )

This year I plan on changing chainplates, checking/changing thru hulls, and getting the bottom painted.

The interesting thing I noticed in the link was this first statement... "With the boat out of the water..." So that answers the practicality of lubricating seacocks while the boat is IN the water.

BTW I keep my seacocks closed when I am not on the boat... every one. I also exercise the seacocks about once a month. And certainly the raw water intake for engine cooling is exercised more often than that.