I'm can't think of why a well-fitting carbon saddle wouldn't be a good choice for longer rides. Conventional wisdom in the cycling world holds that, provided the shape and position is correctly dialed, less padding tends to equal greater long-term comfort.
It's not a fixed rule for every butt, of course, but it's true for many. Your pelvic bones can carry you all day, but your soft tissues compress, crush... nerves and vessels pinch. Padding tends to spread pressure to those areas; after the 30 minute mark, softer saddles can work against you.
Given that, I'd have to assume that a carbon saddle could carry you to hell and back if it's the right size and shape, and properly dialed. There was a three-way review of the carbon offerings from San Marcos, Italia, and AX Lightness in Bicycling sometime last fall or winter... I seem to recall the article questioning the durability of the San Marcos. The Apollo was a favorite.