I hestitate to make such a mundane suggestion but...why don't you try doing some longer hikes with your dog? One of at least two weeks should let you know whether you enjoy the burden of hiking with your particular dog. Your info says you plan to attempt a thru in 2011, so you've got plenty of time to try it out.
People to talk to about the dogs and hiking include Leigh and Josh of the Hiker Hostel, in Dahlonega, GA. They love dogs and started their AT thru-hike with two of them. To make a long story short, though, when they go on long hikes now, the dog stays home.