(Pashusa, Baratone Brewer) - Have either of you tried to excavate a 5 year old crown? Yes, you need plenty of beer, a pry bar, and a strong back. Once they're established in relatively good soil, some of the tap-roots are as big around as your wrist and somehow manage to penetrate down into the clay beyond a depth of 4 feet + - that's all the further I was willing to dig. Figured that if they were that hearty there was no need to go any further.
Once they're developed to this point, they do have enough root mass and stored carbohydrates to support the excessive vegetation, that's not a real issue. The problem is that there are so many secondary shoots that continue to emerge throughout the Spring and until vegetative growth slows down, that sometimes you get behind in your thinning and the growth gets the better of you. This has happened to me a few times during very wet Springs, and if there's a little Downy Mildew around, it soon becomes A LOT of Downy Mildew and now you have a problem.
Take home point, they're very durable plants and some times we have to do things that we feel are contrary to providing a good harvest, but it's actually better for the health of the plant in the long run. Whack away!