Re: Interlux Schooner vs. Sikkens Cetol
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.