In my prepping of my bike for the beginning of hopefully many many years of touring, I got an idea for panniers. I am thinking of having panniers sewn up for me. I would like to have heavy canvas bag, or out of leather. Has anyone used these materials for bags?

Also I went and rode today I really struggled on some hills. They were not all real bad 2% according to Mapmyride.com but I just struggled on them. I did get up them but I had to drop down to my 25 gear on one. I did manage to average 12 mph today and thats without riding in 2 weeks. Is this all part of cycling, did I just hit a wall today or what?