I'm taking it slow and steady doing about a Bristol-frame worth each fortnight including prog tests. I get up early and commute to London so I get about 2*30 mins each way on the train, then do about another 60-90 mins per eve, which is only when I'm in, which is only about 3 nights per week! 3hrs over the w/e is about average.
From what I've been reading, this level of commitment is definitely not going to get me through, even though at the end of each chapter after a couple of reads I can normally sort out the progress tests.
Like you I've decided that to give myself a decent chance at this I'm going to have to apply myself to it 110% - and with a high responsibility job, working day of 10rs plus 90 mins commuting I just can't see it.
So, I plan to quit my job as early in the NY as I can afford to, and do myself justice. I truly admire those with similar situations to me who manage to put the extreme studying on top of work, but it's not for me.