That kind of "planning" mostly won't work. I've tried to do exactly that but it's really just IMPOSSIBLE to get your planned actions done exactly on planned timeslots. In the end the whole "planning" unravels. GTD makes a lot of sense to me because it completely avoids the problem by detaching actionable items from specific time slots: you just do pre-specified items one by one whenever you can. It doesn't deviate you from long-term plans at all, because you'll put them into "in" list also, and then write out the step-by-step thing to do. The only slight difficulty might be with repetitive items.