They wear out. I’ve seen a few litepro ones and they discolour after a bit due to material loss. Afaik they don’t have wear lines or dimples, so it’s up to the user to decide when to retire the seatpost.
If you're planning to use the bike often or lower your seatpost when folding then we wouldn't recommend this (speaking from experience) it does save amazing weight but titanium would be the route to go,
How do carbon seatposts cope with the constant up and down?