Daisy, 8-12 hours a day sounds about the same for me. I turn my computer on at 6 am when I get up and then turn it off at around 11 or so when I go to bed. Sometimes I turn off the computer when I leave for a few hours, but sometimes I don't. I'll watch a T.V. program then get on the computer, take a walk to the library then come back and get on the computer etc, cook dinner, then I'm back on again before I help with baths and homework etc.
Today I was good instead of getting caught up in emails etc, I wrote first, and kept an article going making web research secondary and I finished the entire article by 11:30 am. So that's a good thing.