To echo what everyone else is saying, try it out on easier hikes and see what works for you. In days gone by (more than I care to think about ... ), I was training for a week long hike in the Grand Canyon. To train, I took my pack and loaded it up with as many Platapus (sp?) water bladders as I could. I then went to a local park with a lot of hills. I spent a lot of time/miles hiking up and down. When you carry bladders like that, if you get tired or something starts to hurt, you can dump water and lighten the pack considerably and get back to your car. FWIW.

LW