Your math is also incorrect. When you put down a base coat of natural teak you apply a minimum of 3 coats IIRC. If you want to clear coat for more durability you put two coats over that so its 5 coats initially, same as varnish. The 18month to two year maintenance coat can be a single coat. I usually put two thinner coats on instead of one, the clear flows better and is more workable with a little bit of thinning. Everything I've read says that varnish needs re coating every six months unless you are at a high latitude. I get two years out of Cetol here in San Francisco, you might get one year out of varnish here but I don't know. I've seen many slightly neglected varnish jobs suddenly start peeling at my marina; not the case with cetol if you heed the warning signs (dull finish, some light surface checking).
I'd say in 8 years I have about 12 coats total including base coat, but only had to re-coat 4 times instead of 8, and prepping is most of the work.
Keel, I don't disagree with you that no matter what you use, prep before coating is the key.
Okay, so my math is wrong...based on the math you gave me. NOW you say that you aren't doing "3-4 thin coats of natural teak beneath 2-3 coats of gloss " every " 18 months " now it is only 2 coats every 18 months.
Varnish takes 2 coats every 12 months. So I see a 50% maintenance time savings.
If you think "5 coats initially" is "the same as varnish", I understand why you think varnish isn't durable, and needs to be redone every 6 months. Varnish is only the most durable and beautiful finish available, IF you don't cut corners.
That is why Cetol was invented.
The teak companionway trim (beside the drink holder on the port side of the companionway,hatch sliders and all of the cabin top hand rails were sanded and varnished in 2010. They are due for a recoat next spring. The door was built and varnished in 2011.
So, four years and three years respectively without needing refinishing. I can live with that level of maintenance.
I would expect I would have to do it twice as often in a lower latitude... in other words, every 2 years.
The only wood trim I touch up annually on our boat is the rubrail, because it gets, er... rubbed.
So, to recap, two coats on the rubrail every year, two coats on the rest of the wood every 4 years.
You are cetoling every 18 months to 2 years.
So, hey, it looks like i was fudging the math as well, because i am not having to refinish ALL of my brightwork every year. just 50% of it.
Keel I am not sure what books you have been reading that condemn varnish to a lifespan of only six months. Casey says 3-5 years for spar varnish, Interlux says 4 years, CLC says 3 years.