I am a night person mostly. I sleep way too much, and have to force myself to get out of bed because I always think I am still tired when I wake up, even if I've slept for 9+ hours.
I sleep when ever. If I go to bed earlier I wake up earlier. If I go to bed later I wake up later. I average 4-5 hours a night and can go the whole day like that. My wife was owning a business and had to get up at 6 so she want to bed at 10 or earlier. If I went to bed with her I was up so freakin early (sunrise is @ about 8:30) I had nothing to do but check this website and play xbox.
It's better for me to time the wake up with her then it is the bedtime.
I'm a night owl but I have to wake up at 6:30 Monday-Friday, so that's not fun. I get about 5 or 6 hrs sleep during the work week and about 8 hrs on Sat. & Sun.