Used Sherwin williams duration on my Fiber cement when I added on/renovated in 2010. Probably repaint this year but it really doesn’t look bad yet. We use either Sherwin Williams or Benjamin Moore 99% of the time on our projects, mostly because of availability in our area.
IMHO, make sure it’s an acrylic latex. Sherwin williams Superpaint is their top of the line I believe and would be a great choice. I’m a GC though, not a painting contractor specifically.
Duration is a “higher grade” than Superpaint, and I think “Emerald” is SW’s highest.
Lotsa painters like the Superpaint better than Duration, though, because the Duration is like painting with pancake batter.
I put some Duration on a deer stand about 7 years ago (out in full sun). It has held up pretty well, but don’t know that it’s THAT much better than Superpaint.
If you’re doing a LARGE job (not just eaves/fascia board), “ease of application” CAN be a big deal...
