They're on for the whole trip (which can start and end at any time unless there's on-time depart/arrival). Our 4:30 departure from SFA was 11:00PM on occasion. LOL and sometimes...NO departure at all!!! There is no crew change (except for engineer) as the one and only 15 minute stop in Florence, SC is for that purpose (and water). There are 6 crews...they work 3 contiguous runs. Shuttled to the Comfort Inn to rest between arrival & departure. They live on either end. I've gone from monthly to cold turkey as of March!!! No "departure" in sight! I miss it.