Yeah it's easy for me to go to bed past 4am now. Whats bad is that it's also easy for me to sleep in past 12pm, even when I DO go to bed earlier. I like to figure that if I go to bed at 4am, I should get up at 12pm, if I go to bed at 12am I should get up at 8am. But it does not work that way. I can go to bed at 12am and still get up at 12pm. I'll feel like crap though from having overslept. so I tend to just stay up late knowing that I'll end up sleeping in anyway. It's a vicious cycle.
Night shifts are the best for me, I stay up all night get home a bit past 7am, I'll be tired enough to fall asleep right away, naturally wake up around 4pm, and get up and feel fully rested and go to work for 7pm. When I need to work lot of OT I always ask to just get a whole bunch of night shifts in a row. I rather work like 10+ nights in a row than days. Days just kill me, due to having to get up early.