I've been spending an average of about 6 hours on each page of my comic. Sometimes a little under, sometimes over. It depends on the detail of the page, whether I struggled much in the sketch stage, and whether I already have a colour palette for the page in question.
Time spent per day: that's a little harder to answer. Some days I'll hyperfocus for hours and still be working at 9pm because I just keep circling back to my iPad. Other days, my brain will ADHD off to nope-ville and I'll get absolutely nothing done. On those days, I'll at least try to spend some time marketing it, since I'm usually procrastinating online anyway. (Once our new public library is finished, I'll be using those days to trot down and read other graphic novels. That'll probably trigger me to at least rough out some page layouts, and the change of environment sometimes helps my brain agree to work.)
Days per week: Usually three. I teach two days a week. The other three working days are supposed to be entirely for illustration. I'm usually too tired to draw after teaching, but I'll let myself draw on weekends when the mood strikes, so a little of my illustration work often dribbles over into them.
Update schedule: At the moment, it's one page each week. Just a standard comic page. I would like to raise that to two pages per week, but I don't have enough of a buffer to feel safe doing that yet. I get busy and exhausted around assessment and reporting time, and I'm easily overwhelmed when I have too much to juggle, so a ten page buffer would be vital. Right now, I have... a two-and-a-sketch page buffer. 
Oh, if you tend to get tension headaches and migraines from your neck muscles pulling, try having a low-dose magnesium supplement each day for a few weeks. It's a muscle relaxant. My partner does this to control such headaches, and it helps him.
