Just chiming in to add that I think another relevent aging factor with Haddo's is the plum brandy topping--fresh I think it is very pronounced, but like everything else it mellows with time. Whether one prefers it at six years out or more like a decade may have something to do with how much of that residual plumminess one enjoys.
As with Stonehaven, I actually prefer Haddo's when it's still young enough to have more of that richness come through--IIRC I've tried it fresh, at five or so years old, and a decade+, and while each have their charms I'm with Josh that my personal sweet spot is Haddo's with enough years to tame the topping, age the tobacco, and marry the flavors, but not so many that it loses its oomph, if that makes sense? Worth noting though that I never had the most sensitive palate and it's only gotten worse, so I may just not be able to appreciate the subtlety of the longer aged stuff.
Obviously the only solution is to try them all for ones self!