AriA, I hear you
While I love
the look of beautifully varnished woodwork, I am a firm believer that unless one can afford to pay another
to keep the varnish
up to scratch, there is no place for clear coating timber above decks!
Having said that, I do have a clear coated laminated tiller (because I just needed at least one bit of varnish in the cockpit
Geoff's advice is good, make covers for everything you can as UV is the killer of varnish.
Next can only be general advice, use top shelf exterior coatings, a least 6 coats (but 8 or 10 is better), perfect preparation and so on.
For instance, for my tiller, it was back to bare wood, 2 very thinned coats of everdure (wet on wet), 4 coats of epoxy
using an UV inhibited hardener (again wet on wet) and then 8 coats of an exterior 2 pack poly clear coat.
I intended to make a sock cover for it but haven't quite managed that yet
. However it is still looking quite good after two and a half years of exposure.
Good luck with your bright-work.