I was reading the same book the other day for the same purpose. I noticed that Lagunitas only dry hops for 3 days. Their Hop Stoopid is one of my favorite IIPA's and isn't lacking in any hop character, so I decided 3 days was enough for me.
Dry hopping is, I assume, like so many other things. The bulk of the desired action occurs early, then tapers off.
I dump my hops prior to kegging just to eliminate clogging. I've been thinking it would be interesting to use one of those large stainless mesh tea infusers filled with hops in the keg just prior to kegging, then just leave it in.