In article ,
says...

Moved into the house 11 years ago.
Back exterior doors looked to be part of a fairly new remodel.
They are solid wood, framing a large glass panels, with what appears to
be a simple poly top coat that has been beaten by sun and rain and
almost completely gone near the bottom.
Yes, I've neglected. Something about a shoemaker's sons. :-)

I want something that will last the longest and withstand the sun and
rain.
I'm toying around with an epoxy product similar to this...
http://www.woodcraft.com/Product/2004140/9248/Mirror-Coat-112-Quart-Kit.aspx
http://xrl.us/bijwr4

I've seen several applications of this and similar products and they
seem to be like virtually dipping the object in plastic. The stuff seems
to be impervious to anything, including sun and water. I wouldn't mind
spending a hundred bucks on this stuff it it's going to protect like I
think it will.

Has anyone used it in an exterior application?

Epoxy has no more innate immunity to UV than any other coating--the
manufacturer says specifically that it will yellow in exterior exposure
which implies that it doesn't have the heavy dose of UV barrier that a
coating intended for exterior use would have.

Take a look at
http://www.jamestowndistributors.com...uct.do?pid=869
&familyName=AwlBrite+Clear+Gloss+Base, which is specifically intended
for exterior use under harsh conditions.