On your Dornish economic plan, how long would it take to pull the Torrentine into that valley and make it fertile? One generation, two? Your plans are great but can be undercut by having stupid kids (Quellon, Viserys II, etc) seeing the desert bloom and a forest of acacia rising up agaist the red sands has a dramatic effect.

At least a generation, and likely more than one, although it’s likely an iterative process where you’re gradually diverting more and more water and pushing it out further and further, so it’s not like you only receive the benefits at the end of the process. 

But yes, that’s always a danger with elite-directed reform, especially in systems where political power is inherited. Unlike more broad-based systems, where you have institutions that can provide continuity of policy far longer than the span of a human life, you get these sudden and often wrenching changes when there’s a change in personnel (as it were).