Is it possible for a RN to work five 12 hr days?

Yep. I've done it, but I wouldn't recommend it (unless that's your normal schedule, and it allows you to have more days off in a row). If you're talking about overtime, I wouldn't do it regularly; you will be burnt to a crisp in no time. I've been doing OT regularly for the past few months, and I think I've reached my peak for a little while. I think I have one more I signed up for, but I'm recognizing that it's just not worth it, so no more, at least for a while. I value my days off too much.

I've worked 5 12-hour shifts in a row twice since I started and they just about kill me. It's usually a Friday-Tuesday and I have a few days off afterwards, but it's still not worth it. By that last shift I am so tired and burnt out. But it is doable lol

You could do itonce ina while but not all the time. You wouldn't find a job that would schedule it li9ke that all the time.You would get fried really quickly.

I once worked in an ICU that worked seven (7) twelve-hour shifts in a row~ one week on, one week off. Most people liked it, because they enjoyed having that week off, every other week, but I refused to do it to myself. I worked five (5) twelves in a row, two days off, then two on, five off. I did that for 8 years! Yes, you get tired and feel like you never have time to recuperate. I don't know how the other nurses did it, working seven 12's in a row. But they thought I was nuts to not want to do it!

A century ago, the STANDARD work schedule was 5-12 hour shifts PLUS a half shift on Saturday. No paid vacation, no paid sick time.

No judgement, just sayin'.

How long is your commute? I ask that because a 12 hour shift is just the time spent working. It doesn't include lunch, getting in a little early(traffic can be unpredictable), leaving later than expected some days, and the commute there and back.
My actual door-to-door time is more like 14 hours.

Yes it is. Nurses where I work, in Eagle Pass Texas at Fort Duncan do it all the time regularly. In fact most of them work five 12 hr shifts. Myself, I prefer to only work 4 but most of the time my boss schedules everyone for five. It is common for us, and only if you are on orientation will the boss schedule 3 days only. We are usually perpetually short-staffed hence the five day per week schedules.

Possible, but not healthy -- and probably not safe for the patients. Studies have shown that people who are tired, have not gotten enough sleep, work too many hours in a row, etc. make more mistakes than people who are well-rested.

Of course it's possible. Some people do it often, others never.