Think my longest ride with my messenger bag was about 35 miles. It wasn't too bad except on the way back I was carrying an extra pair of drop bars in the bag and they were poking me in the back a little. Besides that every ride with my messenger bag has been preferable to the backpack I used to use. I usually try to pack light whenever possible though, rather use just a butt pack to cut down on weight and keep the sweat off my back.