When we had the addition to our house done we had a custom made Mahogany double door made and this was the product that was recommended by both the manufacturer of the door and the local company that we had finish the door.
I've seen that product, how has it held up? Is it exposed to much sunlight?
White oak doesn't hold up well with just varnish. It will fail in a few years. The best I've seen is to saturate it really well with a marine epoxy, such as WEST system, THEN coat well with a quality marine polyurethane or varnish. The epoxy will adhere better to the oak; the marine poly will protect the epoxy from UV light.

I seem to recall an article on outdoor finishing and your idea of spar var over epoxy was deemed to be the best way to get a lasting finish.White oak doesn't hold up well with just varnish. It will fail in a few years. The best I've seen is to saturate it really well with a marine epoxy, such as WEST system, THEN coat well with a quality marine polyurethane or varnish. The epoxy will adhere better to the oak; the marine poly will protect the epoxy from UV light.
