Like the answer to every question, it depends.
How much traffic does the boat get inside?
Are we talking grab-holds or bulkheads?
Cold climes or hot?
A good varnish job will last twenty years, inside, and not used hard. A quickie can look old in three months.
I don't like the feel of oil finish teak inside, so do not know how long it would look good. I suspect that oil finish gets tired looking fast.
I refinished the inside of my Whitby with Bristol finish (11 gallons) and it still looks the same as it did when I finished the job. However I will not use it again. The cost is too high and it is dificult to use. I got no help from the maker, when problems came up.
I have started using Helmsmen from Minwax. But have not had it on anything long enough to say if it's good or bad. There are others here in the Keys that are having success with it outside. Like all varnish, it depends more on the applcation than the product.
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