Doing 12 hour shifts is better in some ways - I get a mixture of weekends (socialising) and weekdays off (shopping is infinitely more bearable on a weekday) so best of both worlds, as well as 4-6 days off between shift sets (bar the one where I do 3 days then 3 nights straight after) so there's no need to cram everything into two days when the rest of the world is doing the same. Compare that to dealing with a commute 5 days a week and still not having a lot of free time in the evenings, and only 2 days off... I think the 9-5, Mon-Fri thing is a bit archaic and I believe there are studies showing it's not a particularly good pattern for productivity.
Just me, Clubland TV and the coffee machine... roll on 8am.