There are, of course, economic and political motives behind this. Economically, the plan will be to reassure the markets that the coalition has a deliberate plan which extends beyond the next few months (which was a major consideration behind the IFS's suggestion that the spending review be extended to five years, instead of three). And, politically, the hope is that previewing the gain which follows the pain will keep the public on board with it all.
Wonkishly speaking, it will be intriguing to see whether this approach affects how subsequent Budgets are handled. After all, the further Osborne roams into the long-term tomorrow, the less room for manoeuvre he has in future. Not that this is necessarily a bad thing, you understand. After years of volatile, deceptive and short-termist Budgets from Brown, we could do with a few that feel more like financial progress reports.