You can figure out things in the short term that way, but if you want to know if the marginal money will be used in a year, you'll have to know every project they run in the mean time and how much each will cost. This will include projects that haven't even been planned yet.

This isn't a train that doesn't hold close to its time table. This is a train that leaves when it seems like a good idea. And you're trying to predict the time to within a few minutes weeks ahead of time. You won't even be able to predict which train you'd catch.