I'm coming up on two years of 24/7 direct weather exposure on the exterior finishes with zero maintenance during that time. Late last summer the top of the toe and cap rails started to haze a little. Happy to report that the finish didn't fail over the winter. Consequently, I've begun recoating everything that can be brought back to my shop. The toe rail will have to wait for May/June weather.
I chose the varnish over epoxy method banking on the extended recoat schedule. So far I'm satisfied considering most varnish only recoats are done bi-annually.
FWIW: I used System 3 Silver Tip laminating epoxy(2 coats) followed by 5-6 coats of the S3 gloss spar varnish.
On interior window sills I've used McKlosky satin spar(light thinned) as a wiping varnish with great results. I've also used Watco satin wiping varnish on interior surfaces that don't see a lot of UV such as cabinet doors in the head.
Please throw me the bowline Fraulein!