Is better to practice a little bit everyday or a lot just once in a week?
A little bit everyday, then once you get to intermediate level, it's better just to do once a week, since most of time it's thinking more so than drawing.
A little bit every day.
An hour a day for 7 days is better than a 12 hour marathon once per week in my opinion. Also a little bit every day is better for building a routine, and gradually increasing it when you have time.
I also disagree with >>2877716 that once a week is better for intermediates.