One can do two very different things with blending:
* produce essentially the same predictable product year after year;
* take a component or set and produce the best overall wine around that core.
What I see Dave doing is the latter and this is why we get a number of different wines from him every year, each with its own individual character, even though there is some overlap in ingredients.
As to whether to cross the estate/neighbor boundry, that is a tough
call and one with arguments on both sides. Certainly there is interest
in "preserving the line" of estate wines, especially to the degree that
they have a character which is different from the neighbor's wine, even
when vinified by the same hand. But, I can also imagine myself standing
asking "Should I keep the line pure, or should I make a better wine?" and, unless you are more interested in the label than the contents like some of those N**a types, it is hard not to vote for the better wine.
Tough call. I'm sure Dave wishes he could do it both ways and see how it comes out and then decide, but that is not one of the choices!