obviously there's no right answer and what works for one might not work for someone else, but if you approach subjects sequentially, by the time you do your first exam sitting, you will have forgotten everything about the subjects #1 and #2 already.. Having my ATPLs done and dusted I honestly think you have to follow the modular approach - tackle 4-6 subjects at a time and do them in parallel, taking bits and pieces from each subject at a time..
as for the time lines - it's whatever you can afford. I'm in full time employment + I wanted to throw hour building in the mix too. Around winter time I spent around 2-3 hours a day, bout 4 days a week.. in the summer time there was less studying and more flying. done them all, first time passes, in 18 months time
your mileage will vary.