As others have stated, 24s are awesome if you are in a station, and are slow (my definition of slow being less than 8 calls average in 24 hours). They would never work where I work, where we average 18 calls in 12 hours. If you are in a station, with a bed, and get enough down time/sleep time, than there is nothing wrong with working a 24. esp if you can sleep during the day when all you other chores have been completed.
8s suck, commuting 5 days a week gets old, esp when you get used to working 3 and 4 days a week.
I have to admit, I would gladly take a 24 hour truck where you do 0-1 call a shift. If you pay me well, give me good benefits, than I will smile happily, take a long nap, and work on side projects at the station. But I would have to pick up a side job or OT on a busy 12 hour truck just to maintain my sanity.
btw, the reason most places start their 24s at 0700ish is so the crew can sleep at night, and the well rested crew can come in and do their chores, and the sleeping crew can go home. if the shift change was at noon, the night crew would want to sleep until noon until they go home.
Our bussiest time period is typically between noon and 6pm during the week, and 10pm and 2am 7 days a week.
We I think our agency does about 70,000 runs a year, with between 10 and 15 units on over 24 hours. kinda hard to get a good nights sleep when you are that busy.