What is best protection for window trim in a bathroom?

[dennis thompson]

I am having my bathroom painted. There is a window in the shower with wood trim around it that appears to be stained with polyurethane over it. It will be painted white. The painter and I are worried that the wood will rot (it's built into the tiles so it cannot easily be removed and replaced with azek).
I am thinking over what to put over the paint....polyurethane? spar varnish? etc.? The painter suggested a small curtain over the whole window, that was very quickly rejected by my wife so that is NOT an alternative.
Thanks

[Jerome Stanek]

why not a good exterior finish paint

[dennis thompson]

Jerome
Brilliant,sometimes the simplest solution is staring me right in the face and for some reason I don't see .
Thanks

[Mike Hollingsworth]

why not a good exterior finish paint

4 coats of Latex.
If it's thick as a bandaid it will flex and seams will never crack.

[Bruce Wrenn]

Can trim be replaced with PVC trim, then painted?

[Andrew Pitonyak]

How difficult is it to remove the existing paint? if you can do this, then I would use a penetrating epoxy on the wood. After that, I would prime and paint using the toughest most durable paint that I could find. I have some stuff used by boat builders. I applied it to some "funky" wood on external trim that is now holding up just fine.I also used it on an outdoor swing seat, and a "park bench" that I refinished a few years back. I am a fan.

When I had lots of trim damage, I simply removed the trim and replaced it with fake wood.

[Robert Engel]

Have you considered Azak? It is available in several trim varieties.