I have been in Europe for about 12 days and have been touring with my son (9 years old). We will continure our trek for the next 5 weeks. I just thgouth I would drop some advise. Before I left I asked all the same questions you are asking. Like what pack should I buy. The best advise the I recieved was buy one the fits well. I also heard do not buy a pack larger then 3500 ci or so. I am here to tell you that is plain wrong. I bought the Eagle Creek Ultimate with a 5700ci size. I have seen dozens of people with the smaller Continental or similar sized packs at 3800 ci. They not only have their pack busting at the seams they are carrying two to three plastic bags or small gym type bags. I am sure these people thgouth they had a big enough bag, but either got bad advise or bought the wring bag. My advise is to go larger they you need and pack light.