Should I seal the ends of large fir beams?

I have four 16x4 fir beams sticking out of the side of my house. I'm in the process of "renewing" them, which includes cutting them back a bit. So I end up with a new end, and I wondered what if anything I should do to seal the end-grain other than just prime and paint. These beams are out in the sun and rain, with nothing above them.

I'm using Abatron Liquid Wood and WoodEpox to consolidate and fill in on the top and sides where there's some rot, so I could use Liquid Wood on the end grain. That would put a layer of hard epoxy on the end that has soaked into the grain a bit, and I believe make it impervious to water. And then of course primer and paint on top of that. That might make for a very long- lasting surface.

But I'm not sure that's the best thing to do. Maybe wood is supposed to breathe.

Does anyone here have any experience dealing with this issue? What do you think?

The epoxy sounds like an interesting idea. My only doubt with that is that those products are fairly new, so it's hard to know whether it will turn out to provide good protection years later. The products I've seen say you can paint them, but the surface is not porous, so paint on top of that is not going to serve anything other than a cosmetic role. Thus you'd be depending entirely on the epoxy sealer., and on no moisture getting in behind it.

I would at least prime them with linseed oil primer. (Don't use water-base primer. It doesn't soak in.) Personally I'd be tempted to add some extra linseed oil to the primer. Current paints are not what they used to be, and exposed ends was never a good idea in the first place.

Fir is fairly tough but it will rot if exposed. There's no reason for it to "breathe". (If you look at hardwood stock in lumber yards you'll see that much of it is sealed on the ends with wax, to prevent excessive moisture uptake, which could cause warping.)