"the longest day"
When I first became an RN over 18 years ago...shifts were 8 hours and a double was 16 hours. Now...most hospitals work 12 hours and doubles for the most part don't happen. The max shift as far as I know is 20 hours which is very rare. It does from time to time occur in ICU, ER mostly. Often due to weather or natural diaster or other crisis situations. There is however, a good number of extra hours either required or necessary due to very short staffing. The long hours are hard and even as a young person you will learn quickly that doing these long hours too often will cause "BURN-OUT". Something that happens far too often these days. I have personally as a charge RN in the NICU worked 20 hours and come back in 6 hours and done it all over again DUE TO LOW STAFF and very high acuity. It is a fact of life and will only get worse before it gets better. It is my hope the GOVERNMENT be it state or federal will step in and put a stop to the extra long hours, by regulating mandatory overtime. These long hours promote poor patient care and potentiate errors.

the most worked hours
I used to do 16 hour shifts,it is easy if u don't do them back to back. the most that i have worked contineously was 18hrs straight during a storm,after that i slept for 18hrs!!!!!

My longest shift was 17 hrs, overtime from 12 hr day shift, but picked up many 16hr shifts, and extra night shifts.......labor and delivery, busy shifts with low staffing, and you can't abandon laboring patients, you have to handle them!

12 hour shifts have become very common. I am working with several nurses who work double 8 hour shifts (16 hours total).

I don't know of any hospitals that require double shifts...unless it is an extremely small hospital that has so few nurses it risks having to close.

Shift length
In most states the longest shift you can work is 16 hours. This is state labor law.
In my facility if you ar mandated to work past the end of your shift you are off for the next 10 hours, and get paid for the time off of your next shift that is missed as a result of the mandated overtime. ie: you work 11:00 - 23:30 you are mandated for 4 hours you leave at 03:30 you don't show back up till 13:30. You get paid for the overtime of 4 hours and the 2.5 hours of missed work the next day.

Many facilities can mandate a nurse work extra should staffing require it. When interviewing ask the potential employer if this occurs. In PA(and I would think most states) an RN can't leave unless he/she has a replacement as if you do it's considered abandonment. I worked 12 hour shifts on a Progressive Care Unit and received a day shift sick call. I and the in-house nursing supervisor were unable to find a replacement. After completing my '7P-7A' shift I worked an additional 6-7 hours(the 8 hour evening nurse came in a little early to relieve me). I'll admit it was hard working the extra hours but I managed to stay focused. With any emergency(whether disaster, sick call, weather,etc) many nurses are willing to stay past their shift. But, if you're mandated to do so and you feel unable to do so I would suggest putting your concerns in writing and do the best you can.

looooong shift
i work in the or and my longest shift was ON Call...from Friday night at about 7pm to sunday morning at 7am when...thank god.....i was not on call sunday...and my relief came in....i was verging on "not safe"..it was awful! but goooood money!!! double time...you just go until you can't go no more and then you sleep for 12 hrs...when you are working hard and it is really busy...it goes fast..you just do what you have to do!
good luck