It takes all of two minutes, and that's if you take your time. It's not like it's a huge time commitment. The only time I don't floss is when I'm up until like 3am, but then I usually do it when I get up.
OK you can brush only once a day IF you do a through job and brush a full 5 minutes but it should be at the end of the day.Its takes bacteria 24 hours to colonize enough to begin eroding the teeth.BUT I would recommend brushing after each meal .Before bed use dental rinse to loosen plaque and brush and then floss and then use Listerine to help lessen bacteria buildup while you sleep..A lot of work but a set of teeth well taken care of will last a lifetime.