I work a similar shift pattern, 12.5h shifts, but not 4 on 4 off.
i do fewer days in a row, and less time between shifts.
It goes weekday nights, weekend of days, weekend of nights then weekday days, and then a longer break.
Anyway into the good stuff,
*Good amount of quality time off(full days off means you can get more done)
*Holidays- if you book them round your pattern you can get long breaks for less holiday.
*long shifts, eventually you get used to how long they are and the hours can fly by, especially if you're busy.
*You can leave your work at work (as it says, when your shift is over its over, great if you're having a bad shift/day)
*£££
Negatives
*On a workday there isn't much time for anything else (dependant on how far you travel)
*It will mess with your sleep on your days off.
*Factor in your turnaround time(at the end of your set of night shifts you will want a nap, and will feel pretty lerthargic the rest of the day)
*You'll be working weekends and your days off will fall on weekdays (it can put a strain on relationships)
*You will likely be spending days off alone
I've been working shifts for 2 years, and work with people who have been on shifts for 30. Some people love shifts and the shift pattern, for me, I don't think I want to do them forever, but it works for me at the moment.
I'd say the really important thing is think about how it will affect your out of work life, working long shifts is something you will get used to, and you will figure out how you need to alter your sleeping pattern to get by. But you will have times where it feels like everything outside of work falls on your workdays, so you can miss out on a lot of stuff.
If you have any questions just ask and I'll do my best to answer or ask people I work with who have been on 12h night/day shifts longer.