I work in an ICU. I alternate weeks. 1st week i'll do 3x12, next week is 4x12, then 3, then 4...etc. When I was first starting 12 hour shifts a few years ago I hated it and was so tired that i felt like I couldn't function by the end of the shift. Now that I have worked 12's for a few years in a row i don't believe I would ever want to go back to 8hour shifts. And, like I saw earlier, a 12 hour shift rarely ends up being 12 hours. I work night shift and clock in at 1845 and it's rare if i'm ever out of the building before 0830. In the past I have worked 3x12 and 3x12 2 weeks in a row and still managed to get overtime due to long reports, Drs not being on time in the morning, having a late admission...etc. Currently ICU RNs are mandated to work 12 hour shifts unless special arrangements are made - but even if I was given the option I think I would stay how I am.